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 A129631 #12 Aug 01 2025 14:48:44 %S A129631 2,6,15,20,24,31,34,43,52,61,67,70,76,85,88,91,94,97,103,106,112,115, %T A129631 121,124,127,130,133,136,139,141,145,151,154,160,163,166,169,178,181, %U A129631 190,193,196,199,200,208,211,217,226,229,232,235,238,241,247,250,259 %N A129631 Numbers k such that sum of digits of binomial(k+1, k-1) is a prime. %H A129631 Harvey P. Dale, <a href="/A129631/b129631.txt">Table of n, a(n) for n = 1..1000</a> %e A129631 binomial(6+1,6-1)=binomial(7,5)=7!/(5!*2!)=21 --> 2+1=3 prime. %p A129631 P:=proc(n) local i,k,w; for i from 1 by 1 to n do w:=0; k:=binomial(i+1,i-1); while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(i); fi; od; end: P(1000); %t A129631 Select[Range[300],PrimeQ[Total[IntegerDigits[Binomial[#+1,#-1]]]]&] (* _Harvey P. Dale_, Aug 13 2014 *) %K A129631 nonn,base %O A129631 1,1 %A A129631 _Paolo P. Lava_ and _Giorgio Balzarotti_, May 31 2007