A333932 a(n) is the least integer that is 4-dimensional pyramidal in exactly n ways.

5, 15, 35, 140, 1820, 11375, 820820, 19019000, 10790015600, 1568726956160, 7278234628665, 7271181889157550

Offset: 1

Author

Ilya Gutkovskiy, Apr 10 2020

Keywords

• nonn
• more

Comments

a(n) has exactly n representations as an 4-dimensional pyramidal number P(m, k) = binomial(k + 2, 3)*(k*(m - 2) - m + 6) / 4, with m > 2, k > 1.

Examples

			a(3) = 35 because 35 is the least integer which is 4-dimensional pyramidal in 3 ways (35 = P(3, 4) = P(7, 3) = P(33, 2)).
		

Links

• Index to sequences related to pyramidal numbers

Crossrefs

Cf. A063778, A080852, A261721, A333916.

Extensions

a(9) from Giovanni Resta, Apr 11 2020

a(9) corrected and a(10)-a(12) from Bert Dobbelaere, Apr 14 2020