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A084265
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Modified triangular numbers.
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5
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1, 2, 6, 9, 15, 20, 28, 35, 45, 54, 66, 77, 91, 104, 120, 135, 153, 170, 190, 209, 231, 252, 276, 299, 325, 350, 378, 405, 435, 464, 496, 527, 561, 594, 630, 665, 703, 740, 780, 819, 861, 902, 946, 989, 1035, 1080, 1128, 1175, 1225, 1274, 1326, 1377, 1431, 1484
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| a(n)=A000217(n)+A059841(n)+n. Binomial transform is A084266.
Partial sums give A064843. - N. J. A. Sloane (njas(AT)research.att.com), Jul 20 2008
Starting with "1" = triangle A171608 * the odd integers, (1, 3, 5,...) [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 12 2009]
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FORMULA
| E.g.f.:cosh(x)+exp(x)(2x+x^2/2); a(n)=(n^2+3n+1)/2+(-1)^n/2.
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CROSSREFS
| Cf. A084263.
Cf. A171608 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 12 2009]
Sequence in context: A049634 A120387 A176039 * A084140 A103139 A181025
Adjacent sequences: A084262 A084263 A084264 * A084266 A084267 A084268
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), May 31 2003
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