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 A090009 #23 Feb 24 2024 01:08:04 %S A090009 2,11,11,277,37783,516493,286330897,286330897,56676324799 %N A090009 Begins the earliest length-n chain of primes such that any term in the chain equals the previous term increased by the sum of its digits. %C A090009 From the second term on, subsequence of A[2] := A048519. Due to the "exclusive" definition of this sequence, A048523(1) > a(2), but for k >= 3, a(k) = A[k](1) for A[3..9] = A048524 .. A048527, A320878 .. A320880. - _M. F. Hasler_, Nov 09 2018 %H A090009 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_163.htm">Puzzle 163. P+SOD(P)</a> %e A090009 11 begins the earliest chain 11, 13, 17 of three primes such that any term in the chain equals the previous term increased by the sum of its digits, viz., 13 = 11 + 2, 17 = 13 + 4. Hence a(3) = 11. %o A090009 (PARI) A090009(n,P=2)=forprime(p=P,,P=p;for(i=2,n,isprime(P=A062028(P))||next(2));return(p)) %o A090009 P=0; A090009_vec=vector(6,n,P=A090009(n,P)) \\ Takes long for n > 6. - _M. F. Hasler_, Nov 09 2018 %Y A090009 Cf. A047791, A048519, A062028 (n + digit sum of n). %Y A090009 Cf. A048523 .. A048527, A320878 .. A320880. %K A090009 base,more,nonn %O A090009 1,1 %A A090009 _Joseph L. Pe_, Jan 27 2004 %E A090009 a(7)-a(8) from _Donovan Johnson_, Jan 08 2013 %E A090009 a(9) from _Giovanni Resta_, Jan 14 2013