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Search: id:A145995
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| A145995 |
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a(n) = 8 - 12 n + 5 n^2. |
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+0
2
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| 1, 4, 17, 40, 73, 116, 169, 232, 305, 388, 481, 584, 697, 820, 953, 1096, 1249, 1412, 1585, 1768, 1961, 2164, 2377, 2600, 2833, 3076, 3329, 3592, 3865, 4148, 4441, 4744, 5057, 5380, 5713, 6056, 6409, 6772, 7145, 7528, 7921, 8324, 8737, 9160, 9593, 10036
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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For n > 1, a(n) is square if and only if n-1 is in A081016.
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FORMULA
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a(n)=10*n+a(n-1)-17 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 10 2009]
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EXAMPLE
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A081016(0) = 1 and a(2) = 2^2 = 4; A081016(1) = 6 and a(7) = 13^2 = 169; A081016(2) = 40 and a(41) = 89^2 = 7921; A081016(3) = 273 and a(274) = 610^2 = 372100; A081016(4) = 1870 and a(1871) = 4181^2 = 17480761.
For n=2, a(2)=10*2+1-17=4; n=3, a(3)=10*3+4-17=17; n=4, a(4)=10*4+17-17=40 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 10 2009]
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MATHEMATICA
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Table[8 - 12 x + 5 x^2, {x, 1, 100}]
s = 1; lst = {s}; Do[s += n + 2; AppendTo[lst, s], {n, 1, 450, 10}]; lst [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 11 2009]
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PROGRAM
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(PARI) {for(n=1, 46, print1(8-12*n+5*n^2, ", "))}
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CROSSREFS
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Cf. A081016.
A000217, A080855 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 11 2009]
Sequence in context: A120884 A041859 A022266 this_sequence A018973 A162148 A166781
Adjacent sequences: A145992 A145993 A145994 this_sequence A145996 A145997 A145998
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KEYWORD
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easy,nonn,new
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Oct 26 2008
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EXTENSIONS
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Corrected definition; corrected comment; added example, PARI code and keyword. - Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Oct 29 2008
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