A178155 Partial sums of A003407 (starting at n=1).

1, 3, 7, 17, 37, 85, 189, 471, 967, 2033, 4493, 10621, 23461, 52841, 127745, 340473, 708489, 1367785, 2738841, 5675977, 12313209, 27929825, 66361381, 162909213, 361319381, 780460693, 1722272781, 3904263759, 9528920767, 24294326763, 66213009251, 187941084483, 395937137667, 756194730883, 1395731222259, 2540709556499, 4903320997075, 9814465115099

Offset: 1

Author

Jonathan Vos Post, May 21 2010

Keywords

• nonn

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, ...

Examples

			a(11) = 1 + 2 + 4 + 10 + 20 + 48 + 104 + 282 + 496 + 1066 + 2460 = 4493 is prime.
		

Crossrefs

Cf. A003407.

Formula

a(n) = Sum_{i=1..n} A003407(i).