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 A125772 Primes not of the form j*T_k +/- 1, where T_k is the k-th triangular number greater than 9. 0
 2, 3, 5, 7, 13, 17, 23, 47, 53, 97, 103, 163, 173, 193, 227, 257, 283, 317, 347, 353, 367, 373, 383, 443, 457, 487, 523, 557, 563, 607, 653, 677, 733, 743, 773, 787, 823, 853, 877, 887, 907, 977, 983, 997, 1033, 1097, 1163, 1193, 1213, 1237, 1277, 1283, 1307 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Since all primes would eventually appear in A125765 or A125766 because (p +/-1) times 1(1+1)/2 equals (p +/- 1) let us not use the first triangular number 1. LINKS Table of n, a(n) for n=1..53. EXAMPLE 17 is not of the form j*T_k +/- 1 for any j = 1 or 2 and the triangular numbers, 10, 15 or 21. MATHEMATICA s = {}; Do[m = j*k*(k + 1)/2; If[PrimeQ[m - 1], AppendTo[s, m - 1]]; If[PrimeQ[m + 1], AppendTo[s, m + 1]], {j, 140}, {k, 4, 43}]; Complement[ Prime@ Range@220, Take[Union@s, 200]] CROSSREFS Cf. Complement of A125771. Sequence in context: A033664 A024785 A069866 * A233282 A001000 A094947 Adjacent sequences: A125769 A125770 A125771 * A125773 A125774 A125775 KEYWORD nonn AUTHOR Jonathan Vos Post & Robert G. Wilson v, Dec 05 2006 STATUS approved

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Last modified May 18 16:47 EDT 2024. Contains 372664 sequences. (Running on oeis4.)