

A333916


a(n) is the least integer that is pyramidal in exactly n ways.


2



4, 10, 30, 550, 1540, 48070, 223300, 2634940, 402610950, 1570545340, 13960282700, 5677137442900, 248297918605660
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OFFSET

1,1


COMMENTS

a(n) has exactly n representations as an mgonal pyramidal number P(m, k) = k*(k + 1)*(k*(m  2)  m + 5) / 6, with m > 2, k > 1.
a(12) > 5*10^11.  Giovanni Resta, Apr 11 2020


LINKS

Table of n, a(n) for n=1..13.
Eric Weisstein's World of Mathematics, Pyramidal Number
Index to sequences related to pyramidal numbers


EXAMPLE

a(3) = 30 because 30 is the least integer which is pyramidal in 3 ways (30 is the fourth square pyramidal number, the third octagonal pyramidal number and also the second 31gonal pyramidal number).


CROSSREFS

Cf. A063778, A080851, A261720, A333915.
Sequence in context: A001551 A067142 A145453 * A264564 A304963 A034730
Adjacent sequences: A333913 A333914 A333915 * A333917 A333918 A333919


KEYWORD

nonn,more


AUTHOR

Ilya Gutkovskiy, Apr 09 2020


EXTENSIONS

a(9) from Jinyuan Wang, Apr 10 2020
a(10)a(11) from Giovanni Resta, Apr 10 2020
a(12)a(13) from Bert Dobbelaere, Apr 12 2020


STATUS

approved



