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 A124110 Primes of the form A124080 (10 times triangular numbers) +- 1. 2
 11, 29, 31, 59, 61, 101, 149, 151, 211, 281, 359, 449, 659, 661, 911, 1049, 1051, 1201, 1361, 1531, 1709, 1901, 2099, 2309, 2311, 2531, 2999, 3001, 3251, 3511, 3779, 4349, 4649, 4651, 5279, 5281, 6299, 6301, 6659, 6661, 7411, 8609, 9029, 9461, 9901, 11279 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers j such that A124080(j)-1 is prime or A124080(j)+1 is prime, where repetition means a twin prime, are 1, 2, 2, 3, 3, 4, 5, 5, 6, 7, 8, 9, 11, 11, 13, 14, 14, 15, 16, 17, 18, 19, 20, 21, 21, 22, 24, 24, 25, ..., . - Robert G. Wilson v, Nov 29 2006 LINKS Table of n, a(n) for n=1..46. FORMULA {A124080(j)-1 when prime} U {A124080(j)+1 when prime} = {i = 10*T(j)-1 such that i is prime} U {i = 10*T(j)+1 such that i is prime} where T(j) = A000217(j) = j*(j+1)/2. EXAMPLE a(1) = A124080(1)+1 = (10*T(1)) - 1 = 10*(1*(1+1)/2) + 1 = 10+1 = 11 is prime. a(2) = A124080(2)-1 = (10*T(2))-1 = 10*(2*(2+1)/2) - 1 = 30-1 = 29 is prime. a(3) = A124080(2)+1 = (10*T(2))+1 = 10*(2*(2+1)/2) + 1 = 30+1 = 31 is prime. MATHEMATICA s = {}; Do[t = 5n(n + 1); If[PrimeQ[t - 1], AppendTo[s, t - 1]]; If[PrimeQ[t + 1], AppendTo[s, t + 1]], {n, 47}]; s (* Robert G. Wilson v *) CROSSREFS Cf. A000040, A000217, A028895, A046092, A045943, A002378, A028896, A024966, A033996, A027468. Sequence in context: A005110 A059337 A126240 * A153768 A360181 A092194 Adjacent sequences: A124107 A124108 A124109 * A124111 A124112 A124113 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, Nov 26 2006 EXTENSIONS More terms from Robert G. Wilson v, Nov 29 2006 STATUS approved

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Last modified December 4 03:42 EST 2023. Contains 367541 sequences. (Running on oeis4.)