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 A378917 #27 Dec 16 2024 14:46:19 %S A378917 1,3,4,5,8,11,12,17,18,37,24,53,30,89,39,71,42,101,45,179,57,137,72, %T A378917 193,60,233,84,257,90,251,117,401,123,311,144,373,120,347,105,457,162, %U A378917 661,150,479,180,547,237,599,165,617,264,641,288,683,195,907,231,881,240,773,210 %N A378917 a(n) is the smallest positive integer having n decompositions of twice its value into ordered sums of two odd primes. %C A378917 a(n) is the index of the first n in A002372. %e A378917 For n = 3 we have that the first 3 in A002372 has index 5 and twice 5 is 10 and 10 has 3 decompositions into ordered sums of two odd primes as follows: [3 + 7], [5 + 5], [7 + 3], so a(3) = 5. %o A378917 (PARI) isop(n) = (n % 2) && isprime(n); %o A378917 nb(n) = n*=2; sum(i=1, n-1, isop(i)*isop(n-i)); \\ A002372 %o A378917 a(n) = my(k=1); while(nb(k) != n, k++); k; \\ _Michel Marcus_, Dec 14 2024 %Y A378917 Cf. A002372, A065091, A298990, A378916. %K A378917 nonn %O A378917 0,2 %A A378917 _Omar E. Pol_, Dec 12 2024 %E A378917 More terms from _Michel Marcus_, Dec 14 2024