A133707 Denominator of a remarkable product.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 5, 5, 5, 1, 5, 5, 5, 1, 1, 5, 5, 1, 1, 1, 5, 1, 1, 1, 1, 5, 5, 5, 5, 5, 25, 25, 25

Offset

1,76

Comments

There seems to be no other denominators than 1 or 5^k.

The first 5^k terms appear respectively at positions {76,101,1351,4476,7601,...}

Links

Olivier Gérard, Table of n, a(n) for n = 1..10001

Formula

a(n) = denominator(Product_{i=1..n-1} (394 - 225*i + 85*i^2 - 15*i^3 + i^4)/120).

Mathematica

a[n_]:= Denominator[Product[(394-225 i+85 i^2 -15 i^3+i^4)/120, {i, n-1 }]]; Array[a, 103] (* Stefano Spezia, Feb 08 2025 *)

Crossrefs

Sequence of numerators is in A133706.

Sequence in context: A196998 A232614 A254609 * A171372 A083945 A125563

Adjacent sequences: A133704 A133705 A133706 * A133708 A133709 A133710

Keyword

nonn,frac

Author

Olivier Gérard, Sep 20, 2007

Status

approved