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 A255550 #6 Feb 28 2015 14:49:04 %S A255550 2,5,39,91,199,315,567,829,1227,1513,1953,2569,3277,3769,5119,5925, %T A255550 6607,7539,8319,9375,11007,12511,14103,15801,17593,19165,22213,23617, %U A255550 25467,26967,29347,32733,35809,38085,40953,42915,49093,51787,54055,57459,60409,64057,68433,71637,76299,79719,82545,86133,94921,98037,102745 %N A255550 Main diagonal of array A255551. %C A255550 Equally, 2 followed by the first subdiagonal of A255543. %F A255550 a(n) = A255551(n,n). %F A255550 a(1) = 2; for n > 1: a(n) = A255543(n,n-1). %F A255550 Other identities. %F A255550 For all n >= 1, a(n) = A255553(A083141(n)). %o A255550 (Scheme, two variants) %o A255550 (define (A255550 n) (if (= 1 n) 2 (A255543bi n (- n 1)))) ;; A255543bi is given in A255543. %o A255550 (define (A255550v2 n) (A255551bi n n)) ;; A255551bi is given in A255551. %Y A255550 Cf. A255543, A255551, A255549. %Y A255550 Cf. also A083141, A255410, A255553. %K A255550 nonn %O A255550 1,1 %A A255550 _Antti Karttunen_, Feb 26 2015