A174566 Partial sums of A003214.

1, 2, 4, 7, 13, 23, 43, 80, 156, 308, 628, 1300, 2754, 5908, 12867, 28306, 62914, 140902, 317887, 721397, 1646080, 3773415, 8686867, 20072822, 46541053, 108241285, 252447554, 590284775, 1383498325, 3249679480, 7648547152

Offset: 0

Author

Jonathan Vos Post, Mar 22 2010

Keywords

• easy
• nonn

Comments

Partial sums of number of binary forests with n nodes. The subsequence of primes in this partial sum begins: 2, 7, 13, 23, 43, 317887, 721397, 238855831229, 154308201825571245947273 = a(65).

Examples

			a(34) = 1 + 1 + 2 + 3 + 6 + 10 + 20 + 37 + 76 + 152 + 320 + 672 + 1454 + 3154 + 6959 + 15439 + 34608 + 77988 + 176985 + 403510 + 924683 + 2127335 + 4913452 + 11385955 + 26468231 + 61700232 + 144206269 + 337837221 + 793213550 + 1866181155 + 4398867672 + 10387045476 + 24567374217 + 58196129468 + 138056734916 = 238855831229 is prime,
		

Crossrefs

Cf. A003214.

Formula

a(n) = SUM[i=0..n] A003214(i).