OFFSET
1,2
COMMENTS
Partial sums of number of permutations with no 3-term arithmetic progression. The subsequence of primes in this partial sum begins with 4 in a row: 3, 7, 17, 37, 967, 4493, 66361381, 780460693, 9814465115099, 1094158908254653, ...
FORMULA
a(n) = Sum_{i=1..n} A003407(i).
EXAMPLE
a(11) = 1 + 2 + 4 + 10 + 20 + 48 + 104 + 282 + 496 + 1066 + 2460 = 4493 is prime.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, May 21 2010
STATUS
approved