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A131229 Numbers congruent to {1,7} mod 10. +0
4
1, 7, 11, 17, 21, 27, 31, 37, 41, 47, 51, 57, 61, 67, 71, 77, 81, 87, 91, 97, 101, 107, 111, 117, 121, 127, 131, 137, 141, 147, 151, 157, 161, 167, 171, 177, 181, 187, 191, 197, 201, 207, 211, 217, 221, 227, 231, 237, 241, 247, 251, 257, 261, 267, 271, 277, 281 (list; graph; listen)
OFFSET

1,2

FORMULA

Row sums of triangle A131228.

a(n)=-3+Sum_{k=0..n}{5-(-1)^k} - Paolo P. Lava (ppl(AT)spl.at), Nov 05 2007

a(n) = a(n-2)+10 = 5*n+((-1)^n-7)/2. O.g.f.: x*(1+6*x+3*x^2)/((-1+x)^2*(1+x)) . - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 17 2008

a(n)=10*n-a(n-1)-12 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 25 2009]

EXAMPLE

11 = a(3) = 1 mod 10.

11 = a(3) = row 4 sums, triangle A131228: (1 + 3 + 7).

For n=2, a(2)=10*2-1-12=7; n=3, a(3)=10*3-7-12=11; n=4, a(4)=10*4-11-12=17 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 25 2009]

CROSSREFS

Cf. A128174, A051340, A131228.

Sequence in context: A019365 A078497 A063639 this_sequence A092737 A072669 A108101

Adjacent sequences: A131226 A131227 A131228 this_sequence A131230 A131231 A131232

KEYWORD

nonn,new

AUTHOR

Gary W. Adamson (qntmpkt(AT)yahoo.com), Jun 20 2007

EXTENSIONS

More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 17 2008

More terms from Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 26 2009

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Last modified December 7 08:40 EST 2009. Contains 170430 sequences.


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