The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A179338 Positive integers of the form (10*m^2+1)/11. 5
 1, 91, 131, 401, 481, 931, 1051, 1681, 1841, 2651, 2851, 3841, 4081, 5251, 5531, 6881, 7201, 8731, 9091, 10801, 11201, 13091, 13531, 15601, 16081, 18331, 18851, 21281, 21841, 24451, 25051, 27841, 28481, 31451, 32131, 35281, 36001, 39331 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Here m=(11*(2*n-1)+7*(-1)^n)/4 for n>0. 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) = (110*n*(n-1)+35*(2*n-1)*(-1)^n+39)/4. G.f.: x*(1+90*x+38*x^2+90*x^3+1*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). MATHEMATICA Select[(10Range[300]^2+1)/11, IntegerQ] (* or *) LinearRecurrence[ {1, 2, -2, -1, 1}, {1, 91, 131, 401, 481}, 50] (* Harvey P. Dale, Jul 10 2014 *) PROG (PARI) isok(n) = (((11*n-1) % 10 == 0) && issquare((11*n-1)/10)) \\ Michel Marcus, Jun 07 2013 (MAGMA) [(110*n*(n-1)+35*(2*n-1)*(-1)^n+39)/4: n in [1..50]]; // Vincenzo Librandi, Jul 10 2014 CROSSREFS Cf. A113338, A179088, A179337, A179339, A179370. Sequence in context: A328662 A020235 A046427 * A020238 A220171 A260974 Adjacent sequences:  A179335 A179336 A179337 * A179339 A179340 A179341 KEYWORD nonn,easy AUTHOR Bruno Berselli, Jul 11 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 18 03:39 EDT 2020. Contains 337164 sequences. (Running on oeis4.)