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

1,1

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.

Links

Table of n, a(n) for n=1..12.

Index to sequences related to pyramidal numbers

Example

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)).

Crossrefs

Cf. A063778, A080852, A261721, A333916.

Sequence in context: A056413 A032276 A346890 * A065780 A220480 A105720

Adjacent sequences: A333929 A333930 A333931 * A333933 A333934 A333935

Keyword

nonn,more

Author

Ilya Gutkovskiy, Apr 10 2020

Extensions

a(9) from Giovanni Resta, Apr 11 2020

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

Status

approved