OFFSET
1,6
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..1000
FORMULA
G.f.: -1+(1+x^3/(1-x))*Product_{j>=1} ( 1+x^(3*p(j))/(1-x^(p(j))) ), where p(j) is the j-th prime. - Emeric Deutsch, Jun 27 2009
EXAMPLE
a(12)=6 because we have 3333, 333111, 2^6, 22221111, 2221^6, and 1^(12). - Emeric Deutsch, Jun 27 2009
MAPLE
g := -1+(1+x^3/(1-x))*(product(1+x^(3*ithprime(j))/(1-x^ithprime(j)), j = 1 .. 20)): gser := series(g, x = 0, 75): seq(coeff(gser, x, n), n = 2 .. 65); # Emeric Deutsch, Jun 27 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jun 02 2009
EXTENSIONS
Definition edited to "primes or 1" by R. H. Hardin, Jun 22 2009
STATUS
approved