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 A179339 Positive integers of the form (30*m^2+1)/11. 5
 11, 221, 461, 1091, 1571, 2621, 3341, 4811, 5771, 7661, 8861, 11171, 12611, 15341, 17021, 20171, 22091, 25661, 27821, 31811, 34211, 38621, 41261, 46091, 48971, 54221, 57341, 63011, 66371, 72461, 76061, 82571, 86411, 93341, 97421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Here m = (11*(2*n-1)+3*(-1)^n)/4 for n>0. More generally, (t*((11*(2*n-1)+k*(-1)^n)/4)^2 +1)/11 = ( 22*t*n*(n-1) +t*k*(2*n-1)*(-1)^n+(t*(k^2+121)+16)/22 )/8 for any natural number t == 2, 6, 7, 8, 10 (mod 11) and k = -5, -1, -9, 3, 7, respectively. LINKS B. Berselli, Table of n, a(n) for n = 1..10000. Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1). FORMULA a(n) = (330*n*(n-1)+45*(2*n-1)*(-1)^n+89)/4. G.f.: x*(11+210*x+218*x^2+210*x^3+11*x^4)/((1+x)^2*(1-x)^3). a(n) = a(-n+1) = a(n-1)+2*a(n-2)-2*a(n-3)-a(n-4)+a(n-5). CROSSREFS Cf. A113338, A179088, A179337, A179338, A179370. Sequence in context: A298889 A204236 A035012 * A055411 A341491 A064093 Adjacent sequences:  A179336 A179337 A179338 * A179340 A179341 A179342 KEYWORD nonn,easy AUTHOR Bruno Berselli, Jul 11 2010 - Dec 10 2010 STATUS approved

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Last modified August 15 08:37 EDT 2022. Contains 356132 sequences. (Running on oeis4.)