A121660 -id:A121660 - cp's OEIS frontend

1, 6, 55, 556, 7839, 118141, 2488800, 54871741, 1374282325, 35786212191, 1182319284628, 40234641889543, 1409394785418633, 53597236487797597, 2091701617809524916, 96271871655725943733, 4719413412748380767833

Offset: 1

Jonathan Vos Post, Aug 14 2006

dead

Previous name was: Denominator of fraction equal to the continued fraction [4, 6, 9, ..., semiprime(n)].

Numerator of fraction equal to the continued fraction [4, 6, 9, ..., semiprime(n)] is A121660. Hence A121660/A121661 is semiprime analog of A036247/A036248.

			a(1) = denominator of 4 = 1.
a(2) = denominator of 4 + 1/6 = denominator of 25/6 = 6.
a(3) = denominator of 4 + 1/(6+1/9) = denominator of 229/55 = 55.
a(10) = denominator of 4+1/(6+1/(9+1/(10+ 1/(14+1/(15+ 1/(21+1/(22+1/(25+1/(26))))))))) = denominator of 149001936472/35786212191 = 35786212191.

A121661 := proc(n) local x,i ; x := A001358(n) ; for i from n-1 to 1 by -1 do x := A001358(i)+1/x ; end do: denom(%) ; end proc: # R. J. Mathar, Jun 29 2011

a(n) = A118836(n). - Georg Fischer, Nov 02 2018

cp's OEIS Frontend

A121661 Duplicate of A118836.

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