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Search: id:A152950
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| A152950 |
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a(1)=3; then add 1 to the first number, then 2,3,4... and so on. |
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+0
1
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| 3, 4, 6, 9, 13, 18, 24, 31, 39, 48, 58, 69, 81, 94, 108, 123, 139, 156, 174, 193, 213, 234, 256, 279, 303, 328, 354, 381, 409, 438, 468, 499, 531, 564, 598, 633, 669, 706, 744, 783, 823, 864, 906, 949, 993, 1038, 1084, 1131, 1179, 1228, 1278, 1329, 1381, 1434
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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basic/fundamental/general sequence(s), similar to Triangular numbers (A000217).
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FORMULA
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a(n)= A152949(n+1) = 3+A000217(n-1). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 03 2009]
a(n) =3+C(n,2), n>=1. [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 12 2009]
a(n)=n+a(n-1)-1 (with a(1)=3) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 07 2009]
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EXAMPLE
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For n=2, a(2)=2+3-1=4; n=3, a(3)=3+4-1=6; n=4, a(4)=4+6-1=9 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 07 2009]
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MATHEMATICA
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s=3; lst={3}; Do[s+=n; AppendTo[lst, s], {n, 1, 5!}]; lst
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PROGRAM
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(Other) SAGE: [3+binomial(n, 2) for n in xrange(1, 55)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 12 2009]
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CROSSREFS
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Cf. A000217, A152947, A000124, A152948, A152949
Sequence in context: A140570 A032720 A090867 this_sequence A005626 A030712 A025000
Adjacent sequences: A152947 A152948 A152949 this_sequence A152951 A152952 A152953
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KEYWORD
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nonn,new
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AUTHOR
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Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 15 2008
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