Values of n such that n^2 + 5 is a triangular number (A000217).

Terms

a(0) =1a(1) =4a(2) =10a(3) =25a(4) =59a(5) =146a(6) =344a(7) =851a(8) =2005a(9) =4960a(10) =11686a(11) =28909a(12) =68111a(13) =168494a(14) =396980a(15) =982055a(16) =2313769a(17) =5723836a(18) =13485634a(19) =33360961a(20) =78600035a(21) =194441930a(22) =458114576a(23) =1133290619a(24) =2670087421a(25) =6605301784a(26) =15562409950a(27) =38498520085a(28) =90704372279a(29) =224385818726