A305984 a(n) = Product_{d|n, d>1} prime(A305793(1+d)-1), where A305973(k) records the prime signature of 2k-1.

1, 2, 2, 6, 2, 8, 5, 12, 4, 20, 2, 72, 7, 20, 8, 60, 5, 32, 5, 120, 20, 44, 2, 432, 10, 28, 20, 300, 2, 320, 11, 300, 8, 50, 20, 576, 11, 50, 28, 3120, 2, 800, 5, 264, 80, 20, 5, 4320, 55, 200, 20, 1428, 2, 320, 20, 1200, 50, 44, 5, 17280, 5, 154, 80, 1500, 28, 1760, 19, 300, 8, 2000, 5, 17280, 11, 44, 80, 1650, 50, 448, 5, 78000, 40, 68, 2

Offset: 1

Author

Antti Karttunen, Jun 15 2018

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..8192

Crossrefs

Cf. A305973, A305982, A305985 (rgs-transform).

Programs

PARI

A305984(n) = { my(m=1); fordiv(n, d, if((d>1), m *= prime(A305973(1+d)-1))); (m); }; \\ Needs also code from A305973.

Formula

a(n) = Product_{d|n, d>1} A008578(A305793(1+d)).