A001684 From a continued fraction. (Formerly M1693 N0669)

1, 1, 1, 1, 2, 6, 30, 390, 32370, 81022110, 79098077953830, 2499603048957386233742790, 6399996109983215106481566902449146981585570, 1296147136591533261616288032775924136752630487513536584267056282299509616710

Offset

0,5

References

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

John Cerkan, Table of n, a(n) for n = 0..17

V. C. Harris, Another proof of the infinitude of primes, Amer. Math. Monthly, 63 (1956), 711.

Formula

a(0) = a(1) = a(2) = 1, a(n) = Product_{k=0..n-3} A001685(k) for n >= 3. - Sean A. Irvine, Nov 13 2012

Example

For n=7, A001685(0..4) = 1, 2, 3, 5, 13, so a(n) = 1*2*3*5*13 = 390. - Michael B. Porter, Nov 29 2025

Crossrefs

Sequence in context: A242996 A127815 A054934 * A076926 A092023 A112723

Adjacent sequences: A001681 A001682 A001683 * A001685 A001686 A001687

Keyword

nonn

Author

N. J. A. Sloane

Extensions

One more term from Sean A. Irvine, Nov 13 2012

Status

approved