OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,0,5).
FORMULA
a(n+1) = a(n) + a(n - n mod 4).
a(n) = A140740(n+4,4).
O.g.f.: (1+2*x+3*x^2+4*x^3)/(1-5*x^4). - R. J. Mathar, May 31 2008
a(n) = (n+1-4*floor(n/4))*5^floor(n/4). - Luce ETIENNE, Aug 05 2015
a(n) = 5*a(n-4) for n>3; a(n) = n+1 for n<5. - Bruno Berselli, Aug 05 2015
Sum_{n>=0} 1/a(n) = 125/48. - Amiram Eldar, Jan 21 2022
MATHEMATICA
Table[(n + 1 - 4 Floor[n/4]) 5^Floor[n/4], {n, 0, 40}] (* Bruno Berselli, Aug 05 2015 *)
LinearRecurrence[{0, 0, 0, 5}, {1, 2, 3, 4}, 40] (* Harvey P. Dale, Jul 01 2022 *)
PROG
(PARI) a(n)=(n+1-n\4*4)*5^(n\4) \\ Charles R Greathouse IV, Oct 07 2015
(Python)
def A140730(n): return ((n&3)+1)*5**(n>>2) # Chai Wah Wu, Jan 18 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, May 26 2008
STATUS
approved