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 A112731 #10 Jul 31 2015 21:45:43 %S A112731 3,13,61,71,83,167,197,241,271,281,283,317,347,349,379,431,457,499, %T A112731 503,569,617,631,641,643,701,757,761,797,827,829,863,1061,1151,1163, %U A112731 1217,1321,1381,1471,1481,1483,1531,1543,1553,1609,1619,1667,1669,1777,1877 %N A112731 Primes such that the sum of the predecessor and successor primes is divisible by 7. %H A112731 Harvey P. Dale, <a href="/A112731/b112731.txt">Table of n, a(n) for n = 1..1000</a> %e A112731 a(1) = 3 because previousprime(3) + nextprime(3) = 2 + 5 = 7. %e A112731 a(2) = 13 because previousprime(13) + nextprime(13) = 11 + 17 = 28 = 7 * 4. %e A112731 a(3) = 61 because previousprime(61) + nextprime(61) = 59 + 67 = 126 = 7 * 18. %e A112731 a(4) = 71 because previousprime(71) + nextprime(71) = 67 + 73 = 140 = 7 * 20. %t A112731 For[n = 2, n < 300, n++, If[(Prime[n - 1] + Prime[n + 1])/7 == Floor[(Prime[n - 1] + Prime[n + 1])/7], Print[Prime[n]]]] (* _Stefan Steinerberger_ *) %t A112731 Prime@Select[Range[2, 298], Mod[Prime[ # - 1] + Prime[ # + 1], 7] == 0 &] (* _Robert G. Wilson v_, Jan 11 2006 *) %t A112731 Transpose[Select[Partition[Prime[Range[7000]],3,1],Divisible[First[#]+ Last[#],7]&]][[2]] (* _Harvey P. Dale_, Jun 11 2013 *) %Y A112731 Cf. A000040, A112681, A112794, A112731, A112789, A112795, A112796, A112804, A112847, A112859, A113155, A113156, A113157, A113158. %K A112731 easy,nonn %O A112731 1,1 %A A112731 _Jonathan Vos Post_, Dec 31 2005 %E A112731 More terms from _Stefan Steinerberger_ and _Robert G. Wilson v_, Jan 02 2006