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A349251
a(n) is the integer reached after repeated application of the map x->A349194(x) or -1 if this process does not terminate.
1
1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 4, 6, 8, 1, 3, 5, 7, 9, 4, 8, 9, 3, 6, 9, 6, 3, 9, 9, 9, 9, 7, 4, 3, 4, 6, 9, 7, 6, 48, 3, 5, 9, 3, 7, 9, 5, 5, 9, 9, 3, 9, 3, 48, 9, 9, 9, 9, 6, 9, 9, 3, 5, 9, 3, 9, 9, 9, 9, 6, 8, 9, 9, 9, 9, 9, 5, 8, 9, 9, 7, 9
OFFSET
1,2
COMMENTS
Heuristics suggest that numbers n such that a(n) = -1 have density 1 and may be quite dense by 10^10. - Charles R Greathouse IV, Nov 15 2021
LINKS
EXAMPLE
For n=19, A349194(19) = 10 and A349194(10) = 1 and 1 is a fixed point of A349194 (see A349190), so a(19)=1.
MATHEMATICA
f[n_] := Times @@ Accumulate @ IntegerDigits[n]; a[n_, itermax_] := Module[{m = FixedPoint[f, n, itermax]}, If[f[m] == m, m, 0]]; itermax = 100; Table[a[k, itermax], {k, 1, 100}] (* returns 0 if the number of iterations exceeds itermax, Amiram Eldar, Nov 12 2021 *)
PROG
(PARI) f(n) = my(d=digits(n)); prod(i=1, #d, sum(j=1, i, d[j])); \\ A349194
a(n) = {my(nb=0); while (1, my(m=f(n)); nb++; if (m==n, return (m)); if (nb > 100, return (0)); n = m; ); }
CROSSREFS
Sequence in context: A128244 A010888 A177274 * A131650 A033930 A076314
KEYWORD
nonn,base
AUTHOR
Michel Marcus, Nov 12 2021
STATUS
approved