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A087385 a(n) = smallest prime == 1 (mod T(n)) where T(n) is the n-th triangular number (A000217). 0

%I #6 May 29 2020 20:08:42

%S 2,7,7,11,31,43,29,37,181,331,67,79,547,211,241,137,307,2053,191,211,

%T 463,1013,277,601,1301,3511,379,2437,1741,1861,1489,2113,1123,2381,

%U 631,1999,4219,1483,2341,821,1723,3613,947,991,6211,12973,1129,3529,7351

%N a(n) = smallest prime == 1 (mod T(n)) where T(n) is the n-th triangular number (A000217).

%e The prime corresponding to the triangular number 21 is 43.

%t sm1[n_]:=Module[{p=NextPrime[n]},While[Mod[p,n]!=1,p=NextPrime[p]];p]; Join[ {2},Table[sm1[(n(n+1))/2],{n,2,50}]] (* _Harvey P. Dale_, May 29 2020 *)

%K nonn

%O 1,1

%A _Amarnath Murthy_, Sep 09 2003

%E More terms from _Sam Alexander_, Dec 28 2003

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)