1,2

Number of symmetric foldings of a strip of <= n stamps. The subsequence of primes begins 3, 5, 23, 41, 61, 1049, 1412351.

Table of n, a(n) for n=1..34.

a(n) = SUM[i=1..n] A001010(i).

a(13) = 1 + 2 + 2 + 4 + 6 + 8 + 18 + 20 + 56 + 48 + 178 + 132 + 574 = 1049 is prime.

Cf. A001010.

Sequence in context: A118403 A033498 A147493 * A147509 A057259 A045599

Adjacent sequences: A178958 A178959 A178960 * A178962 A178963 A178964

nonn

Jonathan Vos Post, Dec 31 2010

approved