A278227 Least number with the prime signature of prime(n)-1.

1, 2, 4, 6, 6, 12, 16, 12, 6, 12, 30, 36, 24, 30, 6, 12, 6, 60, 30, 30, 72, 30, 6, 24, 96, 36, 30, 6, 72, 48, 60, 30, 24, 30, 12, 60, 60, 48, 6, 12, 6, 180, 30, 192, 36, 60, 210, 30, 6, 60, 24, 30, 240, 24, 256, 6, 12, 120, 60, 120, 30, 12, 60, 30, 120, 12, 210, 240, 6, 60, 96, 6, 30, 60, 120, 6, 12, 180, 144, 120, 30, 420, 30, 432, 30, 30, 192, 120, 60, 210

Offset: 1

Author

Antti Karttunen, Nov 19 2016

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A046523.

Cf. also A278228, A278229, A278230.

Programs

Mathematica

Table[Times @@ MapIndexed[(Prime@ First@ #2)^#1 &, #] &@ If[Length@ # == 1 && #[[1, 1]] == 1, {0}, Reverse@ Sort@ #[[All, -1]]] &@ FactorInteger[Prime@ n - 1], {n, 120}] (* Michael De Vlieger, Nov 21 2016 *)

Scheme

(define (A278227 n) (A046523 (+ -1 (A000040 n))))

Formula

a(n) = A046523(A000040(n)-1).