OFFSET
1,1
COMMENTS
a(n) has exactly n representations as an m-gonal 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
Eric Weisstein's World of Mathematics, Pyramidal Number
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 31-gonal pyramidal number).
CROSSREFS
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