A276453 - OEIS

A276453

a(n) = (a(n-1)+1)*(a(n-2)+1)*(a(n-3)+1)/a(n-4) with a(0) = a(1) = 1, a(2) = 2, a(3) = 6.

1, 1, 2, 6, 42, 903, 136052, 881442036, 2581196224947732, 342795531574625708871288171, 5732512385084161208637718426682572229606557631, 5754497648510061274107897581706624823818534711463525598519384262130236399970112

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OFFSET

0,3

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..15

FORMULA

a(n) = A051786(n)*A051786(n+1)*A051786(n+2).

MATHEMATICA

RecurrenceTable[{a[n] == (a[n - 1] + 1) (a[n - 2] + 1) (a[n - 3] + 1)/a[n - 4], a[0] == 1, a[1] == 1, a[2] == 2, a[3] == 6}, a, {n, 0, 11}] (* Michael De Vlieger, Sep 03 2016 *)

PROG

(Ruby)

def A276453(n)

a = [1, 1, 2, 6]

ary = [1]

while ary.size < n + 1

i = a[1..-1].inject(1){|s, i| s * (i + 1)}

break if i % a[0] > 0

a = *a[1..-1], i / a[0]

ary << a[0]

end

ary