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 A118723 #20 Jun 24 2025 10:00:45 %S A118723 2,3,5,7,11,23,29,41,47,59,83,101,113,131,137,149,167,191,227,239,257, %T A118723 263,281,293,311,317,347,353,389,401,419,443,461,479,491,509,563,569, %U A118723 587,599,617,641,653,659,677,743,761,797,821,839,857,887,911,941,947 %N A118723 Chen primes whose digital root is also a Chen prime. %e A118723 167 is in the sequence because (1) it is a Chen prime and (2) the digital root 5 is also a Chen prime. %t A118723 digitalRoot[n_Integer?Positive] := FixedPoint[Plus@@IntegerDigits[#] &, n]; %t A118723 chenPrimeQ[x_] := PrimeQ[x] && Plus@@Last/@FactorInteger[x+2] <= 2; %t A118723 Select[Range[1000], chenPrimeQ[#] && chenPrimeQ[digitalRoot[#]]&] (* _Vladimir Joseph Stephan Orlovsky_, Apr 30 2011, with a function by _Eric W. Weisstein_ *) %o A118723 (PARI) isA118723(n)=[0,0,1,1,0,1,0,1,0][n%9+1]&isprime(n)&bigomega(n+2)<3 \\ _Charles R Greathouse IV_, Apr 30 2011 %Y A118723 Cf. A010888, A109611. %K A118723 base,nonn %O A118723 1,1 %A A118723 Luc Stevens (lms022(AT)yahoo.com), May 21 2006