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A374374
Oblong numbers that are products of smaller oblong numbers.
4
12, 72, 240, 420, 600, 1056, 1260, 2352, 4032, 6480, 7140, 9120, 9900, 10920, 14280, 14520, 18360, 20592, 20880, 28392, 38220, 46872, 50400, 65280, 78120, 82656, 83232, 104652, 123552, 129960, 147840, 159600, 194040, 233772, 245520, 262656, 278256, 279312
OFFSET
1,1
COMMENTS
The oblong number (k^2+2*k)*(k^2+2*k+1) = A047928(k+2) is a term for all k >= 1, because it is the product of the oblong numbers k*(k+1) and (k+1)*(k+2).
EXAMPLE
72 is a term because 72 = 8*9 = 6*12 = (2*3)*(3*4).
1056 is a term because 1056 = 32*33 = 2*2*2*132 = (1*2)*(1*2)*(1*2)*(11*12). (This is the first term that requires more than two factors.)
CROSSREFS
A188660 is a subsequence (only 2 factors allowed).
Sequence in context: A143698 A304164 A199531 * A188660 A047928 A300847
KEYWORD
nonn
AUTHOR
STATUS
approved