OFFSET
1,2
COMMENTS
Partial sums of smallest power of 2 whose decimal expansion contains n. One may see this sequence expressed in binary, rather than decimal, for clarity, though "carries" obscure the characteristic function aspects of structure. The subsequence of primes in this partial sum begins: 3, 311, 1100722116047, 1100722388431.
FORMULA
a(n) = SUM[i=1..n] A030001(i).
EXAMPLE
a(6) = 1 + 2 + 32 + 4 + 256 + 16 = 311 is prime.
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Apr 25 2010
STATUS
approved