A093464 a(1) = 1; for n>1, a(n) = n*a(n-1) - 1 if n is a prime else a(n) = n*a(n-1) + 1.

1, 1, 2, 9, 44, 265, 1854, 14833, 133498, 1334981, 14684790, 176217481, 2290827252, 32071581529, 481073722936, 7697179566977, 130852052638608, 2355336947494945, 44751402002403954, 895028040048079081

Offset

1,3

Links

Table of n, a(n) for n=1..20.

Mathematica

a[1] = 1; a[n_] := a[n] = (p = n*a[n - 1] - 1; If[ PrimeQ[n], p, p + 2]); Table[ a[n], {n, 20}] (* Robert G. Wilson v, Apr 08 2004 *)

Crossrefs

Cf. A093463.

Cf. A000166.

Sequence in context: A260216 A182386 A000166 * A308338 A196301 A375425

Adjacent sequences: A093461 A093462 A093463 * A093465 A093466 A093467

Keyword

nonn

Author

Amarnath Murthy, Apr 05 2004

Extensions

More terms from Robert G. Wilson v, Apr 08 2004

Status

approved