A023571 - OEIS

A023571

Least odd prime divisor of p(n)-3, or 1 if p(n)-3 is a power of 2.

1, 1, 1, 1, 1, 5, 7, 1, 5, 13, 7, 17, 19, 5, 11, 5, 7, 29, 1, 17, 5, 19, 5, 43, 47, 7, 5, 13, 53, 5, 31, 1, 67, 17, 73, 37, 7, 5, 41, 5, 11, 89, 47, 5, 97, 7, 13, 5, 7, 113, 5, 59, 7, 31, 127, 5, 7, 67, 137, 139, 5, 5, 19, 7, 5, 157, 41, 167, 43, 173, 5, 89, 7, 5, 47, 5

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OFFSET

1,6

LINKS

Table of n, a(n) for n=1..76.

MATHEMATICA

Join[{1, 1}, Table[If[IntegerQ[Log[2, n-3]], 1, Select[ Transpose[ FactorInteger[ n-3]][[1]], #>2&][[1]]], {n, Prime[Range[3, 80]]}]] (* Harvey P. Dale, Jul 16 2016 *)

CROSSREFS

Sequence in context: A153613 A356706 A318375 * A160631 A155066 A343480

Adjacent sequences: A023568 A023569 A023570 * A023572 A023573 A023574

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved