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A129895
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a(1)=1. a(n) = a(n-1) + number of triangular numbers among the first (n-1) terms of the sequence.
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1
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1, 2, 3, 5, 7, 9, 11, 13, 15, 18, 21, 25, 29, 33, 37, 41, 45, 50, 55, 61, 67, 73, 79, 85, 91, 98, 105, 113, 121, 129, 137, 145, 153, 162, 171, 181, 191, 201, 211, 221, 231, 242, 253, 265, 277, 289, 301, 313, 325, 338, 351, 365, 379, 393, 407, 421, 435, 450, 465, 481
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| For k=1,3: a(8*n+k) = (4*n+k)*(2*n+1). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 20 2007
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MAPLE
| T := {seq((1/2)*j*(j+1), j = 1 .. 40)}: a[1] := 1; for n from 2 to 60 do a[n] := a[n-1]+nops(`intersect`(T, {seq(a[i], i = 1 .. n-1)})) end do: seq(a[n], n = 1 .. 60); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 21 2007
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CROSSREFS
| Cf. A097602.
Sequence in context: A185603 A046654 A023543 * A096149 A033055 A186390
Adjacent sequences: A129892 A129893 A129894 * A129896 A129897 A129898
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Jun 04 2007
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 21 2007
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