OFFSET
1,1
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
D. H. Lehmer, Draft of Math Review of paper by Om Prakash Srivastava, Sep 18 1957.
Om Prakash Srivastava, On the number of representations as sum of four squares of numbers of the form 4^a(8b+7), Journal of Scientific Research, Banaras Hindu University, VI(2) (1955-1956), 278-285. [Annotated scanned copy]
Index entries for linear recurrences with constant coefficients, signature (0,0,4).
FORMULA
Consists of 55, 79, 95, and the numbers 4^k*m where k >= 1 and m is 7, 15, or 23.
From Colin Barker, Jul 10 2016: (Start)
a(n) = 4*a(n-3) for n>9.
G.f.: x*(28+55*x+60*x^2-33*x^3-128*x^4-145*x^5-204*x^6-128*x^7-12*x^8) / (1-4*x^3).
(End)
EXAMPLE
55 is a member because we have 55 = 49+4+1+1 = 36+9+9+1 = 25+25+4+1.
MATHEMATICA
LinearRecurrence[{0, 0, 4}, {28, 55, 60, 79, 92, 95, 112, 240, 368}, 50] (* Harvey P. Dale, May 06 2019 *)
PROG
(PARI) Vec(x*(28+55*x+60*x^2-33*x^3-128*x^4-145*x^5-204*x^6-128*x^7-12*x^8) / (1-4*x^3) + O(x^50)) \\ Colin Barker, Jul 10 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 09 2016
STATUS
approved