OFFSET
1,1
COMMENTS
The subsequence of primes in this sequence begin: 2, 5, 11, 41, 197, 218363, 3643657.
FORMULA
a(n) = sum[i=1..n] {i such that the Woodall number i*2^i - 1 is prime}.
EXAMPLE
a(6) = 2 + 3 + 6 + 30 + 75 + 81 = 197 is prime. a(33) = 2 + 3 + 6 + 30 + 75 + 81 + 115 + 123 + 249 + 362 + 384 + 462 + 512 + 751 + 822 + 5312 + 7755 + 9531 + 12379 + 15822 + 18885 + 22971 + 23005 + 98726 + 143018 + 151023 + 667071 + 1195203 + 1268979 + 1467763 + 2013992 + 2367906 + 3752948.
CROSSREFS
KEYWORD
hard,nonn,less
AUTHOR
Jonathan Vos Post, Jan 30 2010
STATUS
approved