OFFSET
1,2
COMMENTS
Two decagons appearing at n >= 6. See illustration.
LINKS
Kival Ngaokrajang, Illustration of initial terms
FORMULA
Conjecture: a(n) = 2*a(n-1)-a(n-2)+a(n-4)-2*a(n-5)+a(n-6) for n>7. - Colin Barker, Jan 09 2015
Empirical g.f.: x*(4*x^8-2*x^6-5*x^5-6*x^4-5*x^3-3*x^2-2*x-1) / ((x-1)^3*(x+1)*(x^2+1)). - Colin Barker, Jan 09 2015
PROG
(PARI)
{
a=1; d1=0; p=a; print1(a, ", "); \\5s3b
for(n=2, 100,
if(n<3, d1=2,
if(n<4, d1=3,
if(n<5, d1=5,
if(n<6, d1=7,
if(Mod(n, 4)==0, d1=5,
if(Mod(n, 4)==1, d1=3,
if(Mod(n, 4)==2, d1=7, d1=5
)
)
)
)
)
)
);
a=a+d1; p=p+a;
print1(p, ", ")
)
}
CROSSREFS
KEYWORD
nonn
AUTHOR
Kival Ngaokrajang, Jan 09 2015
STATUS
approved