A113937 Powerful(1) pentagonal numbers: intersection of A001694 and A000326.

1, 9801, 16008300, 94109401, 34346991901, 270990840125, 903638458801, 8676736387298001, 83314021887196947001, 124808911896093027867000, 799981229484128697805801, 37807513098010134416714700, 138451237954843775785881876, 7681419682192581869134354401

Offset

1,2

Comments

a(15) > 10^28. - Donovan Johnson, Jun 28 2011

Links

Table of n, a(n) for n=1..14.

Formula

Solutions to the Diophantine equation b^2*c^3 = d(3d-1)/2. [Charles R Greathouse IV, Jun 28 2011]

Example

94109401=7921*(3*7921-1)/2 is the 7921st pentagonal number and 94109401=89^2*109^2.

Crossrefs

Cf. A001694, A000326.

Sequence in context: A156735 A227489 A350918 * A036353 A174769 A031597

Adjacent sequences: A113934 A113935 A113936 * A113938 A113939 A113940

Keyword

nonn

Author

Giovanni Resta, Jan 31 2006

Extensions

a(8) from Donovan Johnson, Dec 07 2008

a(9) from Donovan Johnson, Jun 20 2011

a(10)-a(14) from Donovan Johnson, Jun 28 2011

Status

approved