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Search: id:A056119
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| 0, 7, 15, 24, 34, 45, 57, 70, 84, 99, 115, 132, 150, 169, 189, 210, 232, 255, 279, 304, 330, 357, 385, 414, 444, 475, 507, 540, 574, 609, 645, 682, 720, 759, 799, 840, 882, 925, 969, 1014, 1060, 1107, 1155, 1204, 1254, 1305, 1357, 1410, 1464, 1519, 1575
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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a(n)=A000096 + 5 * A001477, a(n)=A056115 + A001477 and a(n)=A056121 - A001477 - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 01 2006
a(n) = A126890(n,6) for n>5. - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Dec 30 2006
a(n)=A000096(n) + 5 * A001477(n), a(n)=A056115(n) + A001477(n), a(n)=A056121(n) - A001477(n). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 22 2008
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REFERENCES
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P. Lafer, Discovering the square-triangular numbers, Fib. Quart. 9 (1971), pps. 93-105.
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FORMULA
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G.f.(x)=x(7-6x)/(1-x)^3.
a(n)=C(n,2)-6*n ,n>=13 - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Nov 25 2006
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MAPLE
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a:=n->sum(floor(k+2*n/(k+n)), k=6..n): seq(a(n), n=5..55); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 01 2006
[seq(binomial(n, 2)-6*n , n=13..63)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Nov 25 2006
seq(sum(k, k=7..n), n=6..56); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 22 2008
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CROSSREFS
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Cf. A056115.
Cf. A000096, A056115, A056121, A056000, A001477.
Cf. A000096, A056115, A056121.
Adjacent sequences: A056116 A056117 A056118 this_sequence A056120 A056121 A056122
Sequence in context: A056828 A113505 A076796 this_sequence A082111 A012480 A063611
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, Jul 04 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jul 05 2000
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