OFFSET
1,2
COMMENTS
Numbers satisfying 1 + n*m*(m+1)/2 for three or more values of (n,m), where n >= 0 m > 1.
Numbers in this sequence appear in A101321 at least four times (because the second column contains every positive integer).
LINKS
Daniel Sterman, Table of n, a(n) for a(n)<1000
EXAMPLE
109 is in the sequence because 109 is a centered triangular number, a centered 18-gonal number, and a centered 36-gonal number.
CROSSREFS
KEYWORD
nonn
AUTHOR
Daniel Sterman, Dec 20 2016
STATUS
approved