This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A151981 #14 Sep 08 2022 08:45:38 %S A151981 0,1,16,33,48,49,64,81,96,97,112,129,144,145,160,177,192,193,208,225, %T A151981 240,241,256,273,288,289,304,321,336,337,352,369,384,385,400,417,432, %U A151981 433,448,465,480,481,496,513,528,529,544,561,576,577,592,609,624,625,640,657,672 %N A151981 Numbers n such that n^2 - n is divisible by 48. %C A151981 Numbers congruent to {0, 1, 16, 33} mod 48. - _Charles R Greathouse IV_, Apr 10 2012 %H A151981 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1). %F A151981 From _Colin Barker_, Apr 10 2012: (Start) %F A151981 G.f.: x^2*(1+15*x+17*x^2+15*x^3)/((1-x)^2*(1+x)*(1+x^2)). %F A151981 a(n) = a(n-1) + a(n-4) - a(n-5) for n>5. (End) %F A151981 a(n) = 12*n-(35+3*i^(2*n))/2+(2+2*i)*i^(-n)+(2-2*i)*i^n where i=sqrt(-1). - _Wesley Ivan Hurt_, Jun 07 2016 %p A151981 A151981:=n->12*n-(35+3*I^(2*n))/2+(2+2*I)*I^(-n)+(2-2*I)*I^n: seq(A151981(n), n=1..100); # _Wesley Ivan Hurt_, Jun 07 2016 %t A151981 Table[12n-(35+3*I^(2*n))/2+(2+2*I)*I^(-n)+(2-2*I)*I^n, {n, 80}] (* _Wesley Ivan Hurt_, Jun 07 2016 *) %o A151981 (PARI) a(n)=n\4*48+[-15, 0, 1, 16][n%4+1] \\ _Charles R Greathouse IV_, Apr 10 2012 %o A151981 (Magma) [n : n in [0..800] | n mod 48 in [0, 1, 16, 33]]; // _Wesley Ivan Hurt_, Jun 07 2016 %K A151981 nonn,easy %O A151981 1,3 %A A151981 _N. J. A. Sloane_, Aug 23 2009