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A094180
Numbers k such that 4*k-1 is divisible only by primes of form 4*m-1 (i.e., by the Gaussian primes A002145).
2
1, 2, 3, 5, 6, 7, 8, 11, 12, 15, 16, 17, 18, 20, 21, 25, 26, 27, 32, 33, 35, 37, 38, 41, 42, 43, 45, 48, 50, 52, 53, 56, 57, 58, 60, 61, 63, 66, 68, 70, 71, 77, 78, 83, 86, 87, 90, 91, 92, 95, 96, 97, 100, 105, 106, 108, 110, 111, 116, 117, 120, 121, 122, 123, 125, 126, 131
OFFSET
1,2
LINKS
FORMULA
a(n) = (A094179(n) + 1)/4. - Amiram Eldar, Apr 01 2021
MATHEMATICA
Select[Range[150], AllTrue[FactorInteger[4*# - 1][[;; , 1]], Mod[#1, 4] == 3 &] &] (* Amiram Eldar, Apr 01 2021 *)
PROG
(PARI) {for(n=1, 140, fac=factor(4*n-1); v=vector(matsize(fac)[1], j, fac[j, 1])%4; if(vecmin(v)==3, print1(n, ", ")))} \\ Klaus Brockhaus, May 08 2004
CROSSREFS
For the actual numbers 4*k-1, see A094179.
Cf. A002145.
Sequence in context: A080220 A028778 A284885 * A116545 A140661 A063966
KEYWORD
nonn
AUTHOR
Lekraj Beedassy, May 06 2004
EXTENSIONS
More terms from Klaus Brockhaus, May 08 2004
STATUS
approved