OFFSET
1,1
LINKS
FORMULA
a(n) = 30*n-a(n-1) for n>1, a(1)=25. - Vincenzo Librandi, Aug 07 2010
From Chai Wah Wu, Jun 05 2024: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3) for n > 3.
G.f.: x*(-5*x^2 + 10*x + 25)/((x - 1)^2*(x + 1)). (End)
MATHEMATICA
Do[ If[ !PrimeQ[ n ] && StringPosition[ ToString[ FromDigits[ IntegerDigits[ n, 5 ] ] ], ToString[ FromDigits[ IntegerDigits[ Divisors[ n ] [ [ -2 ] ], 5 ] ] ] ] != {}, Print[ n ] ], {n, 2, 1000} ]
PROG
(PARI) a(n)=([0, 1, 0; 0, 0, 1; -1, 1, 1]^(n-1)*[25; 35; 55])[1, 1] \\ Charles R Greathouse IV, Jun 05 2024
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Robert G. Wilson v, Aug 08 2001
STATUS
approved