A333008 -id:A333008 - cp's OEIS frontend

A333009 Successive differences of A333008 (square roots of perfect squares that are the sum of two nonzero pentagonal numbers).

5, 3, 6, 5, 10, 4, 20, 17, 8, 1, 7, 2, 1, 1, 8, 1, 3, 8, 7, 2, 4, 4, 3, 11, 6, 4, 3, 9, 5, 7, 5, 3, 1, 2, 2, 1, 3, 2, 6, 1, 24, 1, 6, 1, 9, 8, 14, 4, 5, 4, 5, 5, 9, 2, 3, 2, 14, 3, 6, 8, 4, 2, 4, 10, 1, 2, 7, 1, 6, 8, 6, 7, 1, 8, 5, 7, 12, 8, 4, 4, 5, 2, 11, 4

Offset: 1

Olivier Gérard, Mar 05 2020

nonn

The behavior of this sequence is unexpectedly quite complex.

Peter Kagey, Table of n, a(n) for n = 1..1000

Cf. A332986 (analog for indices of triangular numbers).

Cf. A000326, A333007, A333008.

A333007 Perfect squares that are sum of two nonzero pentagonal numbers.

Original entry on oeis.org

36, 121, 196, 400, 625, 1225, 1521, 3481, 5776, 7056, 7225, 8464, 8836, 9025, 9216, 10816, 11025, 11664, 13456, 15129, 15625, 16641, 17689, 18496, 21609, 23409, 24649, 25600, 28561, 30276, 32761, 34596, 35721, 36100, 36864, 37636, 38025, 39204, 40000, 42436, 42849

Offset: 1

Olivier Gérard, Mar 05 2020

			36  = 6^2  = 1  + 35;
121 = 11^2 = 51 + 70;
196 = 14^2 = 51 + 145.

Peter Kagey, Table of n, a(n) for n = 1..1000

Cf. A000326, A332987, A332988, A333008, A333009.

is(k) = issquare(k) && sum(i=1, sqrt(1+12*k)\6, sqrt(1+24*k+12*i-36*i*i)%6==5)>0; \\ Jinyuan Wang, Mar 06 2020

More terms from Jinyuan Wang, Mar 06 2020

cp's OEIS Frontend

A333009 Successive differences of A333008 (square roots of perfect squares that are the sum of two nonzero pentagonal numbers).

Views

Author

Keywords

Comments

Links

Crossrefs

A333007 Perfect squares that are sum of two nonzero pentagonal numbers.

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

PARI

Extensions