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 A343908 a(n) is the least prime == 4 (mod prime(n)). 1
 2, 7, 19, 11, 37, 17, 89, 23, 73, 149, 97, 41, 127, 47, 239, 163, 181, 431, 71, 359, 223, 83, 419, 271, 101, 307, 107, 967, 113, 569, 131, 397, 1237, 421, 2239, 457, 1103, 167, 839, 523, 541, 547, 577, 197, 1777, 601, 1481, 227, 3863, 233, 3499, 2633, 727, 757, 1289, 1319, 811, 1901, 281, 1409 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 EXAMPLE a(3) = 19 because 19 is the least prime == 4 (mod prime(3)). a(4) = 11 because 11 is the least prime == 4 (mod prime(4)). MAPLE a:= proc(n) local q, p; p:= ithprime(n); q:= p; do if irem(q-4, p)=0 then break fi; q:= nextprime(q); od; q end: seq(a(n), n=1..60); # Alois P. Heinz, May 03 2021 MATHEMATICA s = {}; p = 5; Do[q = p + 2; While[Mod[q, p] != 4, q = NextPrime[q]]; AppendTo[s, q]; p = NextPrime[p], {100}]; s PROG (PARI) a(n) = my(p=prime(n)); forprime(q=2, , if (Mod(q, p) == 4, return(q))); \\ Michel Marcus, May 03 2021 CROSSREFS Cf. A000040, A023200 (primes p such that p+4 is also prime), A034694, A035095, A279756. Sequence in context: A368593 A218684 A337614 * A100408 A259370 A103034 Adjacent sequences: A343905 A343906 A343907 * A343909 A343910 A343911 KEYWORD nonn AUTHOR Zak Seidov, May 03 2021 STATUS approved

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Last modified August 12 02:53 EDT 2024. Contains 375082 sequences. (Running on oeis4.)