OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
FORMULA
Conjectures:
a(n) = a(n-1)+2*a(n-5)-2*a(n-6)-a(n-10)+a(n-11) for n>11.
G.f.: x*(1+4*x+5*x^2+3*x^3+12*x^4+x^5+5*x^6+4*x^7+x^10) / ((1-x)^3*(1+x+x^2+x^3+x^4)^2).
PROG
(PARI)
cpg(m, n) = m*n*(n-1)/2+1 \\ n-th centered m-gonal number
cpgr(m, r) = n=1; L=List(); while((t=cpg(m, n))<r, listput(L, t); n++); Vec(L)
cpgcpgs(p, q, r) = setunion(cpgr(p, r), cpgr(q, r))
cpgcpgs(4, 9, 2000)
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Apr 24 2016
STATUS
approved