OFFSET
1,1
COMMENTS
0.1231232331232332333... = sum_{k=0..infinity, 10^(-(k + 3)! / (3! * k!)) * (1 + 10 * sum_{l=2..k + 2, 10^(-(l^2 + l) / 2) * ((10^l - 1) / 3) - 10^(l - 1))}}).
FORMULA
PROG
(PARI) a(n)=sum(k=0, n-1, 1+k-binomial(round(sqrt(2+2*k)), 2)+issquare(8*k+1)*(sqrtint(1+8*k)+1)/2) /* Ralf Stephan, Oct 09 2013 */
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Jiri Klepl, Sep 24 2013
EXTENSIONS
Formula corrected by Ralf Stephan, Oct 09 2013
STATUS
approved