A036248 Denominator of fraction equal to the continued fraction [ 2, 3, 5, ..., prime(n) ].

1, 3, 16, 115, 1281, 16768, 286337, 5457171, 125801270, 3653694001, 113390315301, 4199095360138, 172276300080959, 7412079998841375, 348540036245625584, 18480034001016997327, 1090670546096248467877, 66549383345872173537824, 4459899354719531875502085

Offset: 1

Author

Jeff Burch

Keywords

• frac
• easy
• nonn

Examples

			Prime(4) = 7, and 2+1/(3+1/(5+1/7)) = 266/115, so a(4) = 115. - _Jon E. Schoenfield_, Dec 20 2016
		

Crossrefs

Cf. A000040, A036247.

Programs

PARI

a(n)=if(n<0,0,contfracpnqn(vector(n,i, prime(i)))[2,1])

Formula

a(1) = 1, a(2) = 3, a(n) = A000040(n) * a(n-1) + a(n-2). - Daniel Suteu, Dec 20 2016

Extensions

More terms from Benoit Cloitre, May 25 2003