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A127428 v_5( (10n)! ) - v_5( (5n)! ), where v_p(N) is the p-adic valuation defined in A112765. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
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
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 02 2007
EXTENSIONS
Typo in name corrected by Michel Marcus, Jul 29 2017
STATUS
approved

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Last modified February 28 21:38 EST 2024. Contains 370400 sequences. (Running on oeis4.)