A127428 v_5( (10n)! ) - v_5( (5n)! ), where v_p(N) is the p-adic valuation defined in A112765.

0, 1, 2, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 72, 73, 74, 75, 76, 80, 81, 82, 83, 84, 86, 87, 88, 89, 90, 92, 93

Offset

0,3

Links

Table of n, a(n) for n=0..74.

Formula

a(n) - n = a( [(n+2)/5] ).

Maple

A127428 := proc(n)
    padic[ordp]((10*n)!, 5)-padic[ordp]((5*n)!, 5) ;
end proc:
seq(A127428(n), n=0..100) ; # R. J. Mathar, Mar 29 2017

Prog

(PARI) a(n) = valuation((10*n)!, 5) - valuation((5*n)!, 5); \\ Michel Marcus, Jul 29 2017

Crossrefs

v_5(n) is given in A112765. Cf. A001511, A127427.

Sequence in context: A039244 A160044 A180917 * A039187 A001963 A287183

Adjacent sequences: A127425 A127426 A127427 * A127429 A127430 A127431

Keyword

nonn

Author

N. J. A. Sloane, Apr 02 2007

Extensions

Typo in name corrected by Michel Marcus, Jul 29 2017

Status

approved