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A182759
a(1) = 1, a(2) = 3, for n >= 3; a(n) = the smallest number h > a(n-1) such that [[a(n-2) + a(n-1)] * [a(n-2) + h] * [a(n-1) + h]] / [a(n-2) + a(n-1) + h] is integer.
2
1, 3, 8, 11, 19, 25, 32, 38, 42, 53, 64, 75, 101, 124, 147, 163, 179, 195, 289, 296, 299, 315, 352, 368, 384, 720, 736, 752, 768, 912, 980, 1034, 1066, 1098, 2100, 2132, 2164, 2196, 2289, 2382
OFFSET
1,2
LINKS
EXAMPLE
For n = 5; a(3) = 8, a(4) = 11, a(5) = 19 before [(8+11)*(8+19)*(11+19)] / (8+11+19) = 405 (integer).
MATHEMATICA
nxt[{a_, b_}]:= Module[{h = b + 1}, While[! IntegerQ[((a + b) (a + h) (b + h))/(a + b + h)], h++]; {b, h}]; Transpose[NestList[nxt, {1, 3}, 100]][[1]] (* G. C. Greubel, Jan 23 2018 *)
CROSSREFS
Cf. A182758.
Sequence in context: A154485 A105410 A114548 * A022121 A364086 A171672
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Nov 28 2010
STATUS
approved