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 A092507 #11 Jan 21 2019 19:01:55 %S A092507 2,4,8,18,30,68,128,258,508,1030,2052,4092,8192,16400,32792,65520, %T A092507 131058,262172,524286,1048596,2097156,4194312,8388620,16777210, %U A092507 33554472,67108860,134217738,268435446,536870858,1073741832,2147483616 %N A092507 (Smallest prime >= 2^n) + (largest prime <= 2^n). %C A092507 For n=0 we just take a(0)=2, the least prime >= 2^0, as there is no prime <= 2^0. - _Robert Israel_, Nov 01 2018 %H A092507 Robert Israel, <a href="/A092507/b092507.txt">Table of n, a(n) for n = 0..3317</a> %F A092507 a(n) = A014210(n) + A014234(n) for n >= 2. - _Robert Israel_, Nov 01 2018 %p A092507 [2, seq( (nextprime(2^x-1)+prevprime(2^x+1)),x=1..20)]; # Corrected by _Robert Israel_, Nov 01 2018 %t A092507 PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; Table[PrevPrim[2^n+1] + NextPrim[2^n-1], {n, 31}] (* _Robert G. Wilson v_, Apr 14 2004 *) %Y A092507 Cf. A014210, A014234, A058249. %K A092507 nonn %O A092507 0,1 %A A092507 _Jorge Coveiro_, Apr 05 2004 %E A092507 More terms from _Robert G. Wilson v_, Apr 14 2004