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A047382
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Numbers that are congruent to {0, 5} mod 7.
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0
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0, 5, 7, 12, 14, 19, 21, 26, 28, 33, 35, 40, 42, 47, 49, 54, 56, 61, 63, 68, 70, 75, 77, 82, 84, 89, 91, 96, 98, 103, 105, 110, 112, 117, 119, 124, 126, 131, 133, 138, 140, 145, 147, 152, 154, 159, 161, 166, 168
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Except for the first term, numbers n such that 36*n^2+72*n+35 = (6*n+5)*(6*n+7) is not of the form p*(p+2), with p prime. - Vincenzo Librandi, Aug 05 2010
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FORMULA
| a(n) = 7*n-a(n-1)-9 (with a(1)=0). - Vincenzo Librandi, Aug 05 2010
a(n+1)=Sum_k>=0 {A030308(n,k)*b(k)} with b(0)=5 and b(k)=A005009(k-1)=7*2^(k-1) for k>0. - From DELEHAM Philippe, Oct 17 2011
Contribution by Bruno Berselli, Oct 17 2011: (Start)
G.f.: x^2*(5+2*x)/((1+x)*(1-x)^2).
a(n) = (14*n+3*(-1)^n-11)/4.
a(-n) = -A047352(n+2). (End)
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EXAMPLE
| For n=2, a(2)=7*2-0-9=5; n=3, a(3)=7*3-5-9=7; n=4, a(4)=7*4-7-9=12 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
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PROG
| (MAGMA) &cat[[7*n, 7*n+5]: n in [0..23]]; // Bruno Berselli, Oct 17 2011
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CROSSREFS
| Cf. A008589, A017041.
Sequence in context: A082565 A086255 A171490 * A117140 A031144 A160243
Adjacent sequences: A047379 A047380 A047381 * A047383 A047384 A047385
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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