A320118 - OEIS

A320118

a(1) = a(2) = 1; for n > 2, a(n) = A181819(n) * a(A181819(n)).

1, 1, 2, 6, 2, 24, 2, 10, 6, 24, 2, 144, 2, 24, 24, 14, 2, 144, 2, 144, 24, 24, 2, 240, 6, 24, 10, 144, 2, 80, 2, 22, 24, 24, 24, 54, 2, 24, 24, 240, 2, 80, 2, 144, 144, 24, 2, 336, 6, 144, 24, 144, 2, 240, 24, 240, 24, 24, 2, 1728, 2, 24, 144, 26, 24, 80, 2, 144, 24, 80, 2, 360, 2, 24, 144, 144, 24, 80, 2, 336, 14, 24, 2, 1728

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OFFSET

1,3

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10080

FORMULA

a(1) = a(2) = 1; for n > 2, a(n) = A181819(n) * a(A181819(n)).

MATHEMATICA

Nest[Append[#1, #2 #1[[#2]] ] & @@ {#, Times @@ Prime@ FactorInteger[Length@ # + 1][[All, -1]]} &, {1, 1}, 82] (* Michael De Vlieger, Nov 25 2018 *)

PROG

(PARI)

A181819(n) = factorback(apply(e->prime(e), (factor(n)[, 2])));