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 A180156 #23 Sep 01 2025 11:22:04 %S A180156 1,1,4,2,4,7,6,8,34,12,12,14,13,16,11,19,23,20,24,52,23,40,48,39,58, %T A180156 35,40,41,54,40,60,69,46,41,49,136,172,100,118,91,128,117,71,78,217, %U A180156 126,95,121,99,71,107,120,79,71,144,75,104,78,129,100,74,169,174,116,352,203,238 %N A180156 Sequence from adding the twin primes and dividing by the digit sum of twin primes. %C A180156 If necessary the result is rounded to the nearest integer. %C A180156 This sequence uses round(x) = floor(1/2 + x). - _Jason Yuen_, Sep 01 2025 %H A180156 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TwinPrimes.html">Twin Primes</a> %e A180156 a(7) = round((59 + 61) / (5+9+6+1)) = round(120/21) = round(5.714...) = 6. %e A180156 a(10) = round((107 + 109) / (1+0+7+1+0+9)) = round(216/18) = 12. %t A180156 Floor[1/2+Total[#]/Total[Flatten[IntegerDigits/@#]]]&/@ Select[Partition[Prime[Range[500]],2,1], Last[#]-First[#]==2&] (* _Harvey P. Dale_, Mar 23 2011 *) %t A180156 f[n_] := Floor[1/2 + 2 (n + 1)/(Plus @@ IntegerDigits[n] + Plus @@ IntegerDigits[n + 2])]; f@# & /@ Select[ Prime@ Range@ 1000, PrimeQ[# + 2] &] (* _Robert G. Wilson v_, Aug 16 2011 *) %Y A180156 Cf. A001359. %K A180156 base,nonn,less,changed %O A180156 1,3 %A A180156 _Parthasarathy Nambi_, Aug 14 2010 %E A180156 More terms from _Harvey P. Dale_, Mar 23 2011