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A003458
Erdős-Selfridge function: a(n) is the least number m > n+1 such that the least prime factor of binomial(m, n) is > n.
(Formerly M2515)
3
3, 6, 7, 7, 23, 62, 143, 44, 159, 46, 47, 174, 2239, 239, 719, 241, 5849, 2098, 2099, 43196, 14871, 19574, 35423, 193049, 2105, 36287, 1119, 284, 240479, 58782, 341087, 371942, 6459, 69614, 37619, 152188, 152189, 487343, 767919, 85741, 3017321
OFFSET
1,1
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Jonathan Webster, Table of n, a(n) for n = 1..375 (terms 1..200 from H. C. Williams)
E. F. Ecklund, Jr. et al., A new function associated with the prime factors of C(n,k), Math. Comp., 28 (1974), 647-649.
R. F. Lukes; R. Scheidler; H. C. Williams, Further Tabulation of the Erdos-Selfridge Function, Math. Comput. 66 (1997) 1709-1717.
R. Scheidler, H. C. Williams, A method for tabulating the number-theoretic function g(k), Math. Comp. 59 (199) (1992) 251-257.
Brianna Sorenson, Jonathan P Sorenson, Jonathan Webster, An Algorithm and Estimates for the Erdős-Selfridge Function (work in progress), arXiv:1907.08559 [math.NT], 2019.
Eric Weisstein's World of Mathematics, Erdős-Selfridge function.
MAPLE
A003458 := proc(n)
local m;
for m from n+2 do
if A020639( binomial(m, n)) > n then
return m ;
end if;
end do:
end proc:
seq(A003458(n), n=1..16) ; # R. J. Mathar, Mar 27 2024
MATHEMATICA
f[n_] := Block[{k = n + 2, p = Table[Prime[i], {i, 1, PrimePi[n]}]}, While[ First[ Sort[ Mod[ Binomial[k, n], p]]] == 0, k++ ]; k]; Table[ f[n], {n, 1, 40}]
esf[n_]:=Module[{m=n+2}, While[FactorInteger[Binomial[m, n]][[1, 1]]<=n, m++]; m]; Array[esf, 50] (* Harvey P. Dale, Nov 03 2013 *)
PROG
(PARI) a(n) = local(m, i, f); m=0; i=n+1; while(m<=n, i=i+1; m=factor(binomial(i, n))[1, 1]); i /* Ralf Stephan */
CROSSREFS
Sequence in context: A251532 A251533 A295849 * A133339 A112267 A068985
KEYWORD
easy,nonn,nice
EXTENSIONS
Extended by Robert G. Wilson v, Dec 01 2002
STATUS
approved