OFFSET
0,3
FORMULA
for n>=1, a(25n)=a(25n+1)=a(5n) ; a(25n+2)=a(25n+3)=a(25n+4)=a(25n+5)=5a(5n) ; a(25n+6)=a(n) ; a(25n+7)=a(25n+8)=a(25n+9)=a(25n+10)=a(25n+11)=5a(n) ; a(25n+12)=25a(n) ; a(25n+13)=a(25n+14)=a(25n+15)=a(25n+16)=a(5n+3) ; a(25n+17)=a(25n+18)=5a(5n+3) ; a(25n+19)=a(25n+20)=a(25n+21)=a(5n+4) ; a(25n+22)=a(25n+23)=a(25n+24)=5a(5n+4)
PROG
(PARI) a(n)=denominator((4*n+1)!/5^n)
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Benoit Cloitre, Jan 01 2007
STATUS
approved