login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A072276
Strong pseudoprimes to bases 2 and 3.
7
1373653, 1530787, 1987021, 2284453, 3116107, 5173601, 6787327, 11541307, 13694761, 15978007, 16070429, 16879501, 25326001, 27509653, 27664033, 28527049, 54029741, 61832377, 66096253, 74927161, 80375707, 101649241
OFFSET
1,1
COMMENTS
Composites that pass the Miller-Rabin test for bases 2 and 3. The intersection of A001262 (strong pseudoprimes to base 2) and A020229 (strong pseudoprimes to base 3).
The Washington Bomfim link references a table with all terms up to 2^64. Data from Jan Feitsma and William Galway, see link below, permitted an easy determination of these terms. I tested the Mathematica function PrimeQ[n] with those numbers to verify that it is correct for all n < 2^64. - Washington Bomfim, May 13 2012
LINKS
Joerg Arndt, Matters Computational (The Fxtbook), section 39.10, pp. 786-792
Washington Bomfim, Table of n, a(n) for n=1..1499371 [a large file]
Jan Feitsma and William Galway, Tables of pseudoprimes and related data
A. J. Menezes, P. C. van Oorschot and S. A. Vanstone, Handbook of Applied Cryptography, section 4.2.3, Miller-Rabin test.
Eric Weisstein's World of Mathematics, Rabin-Miller test
MATHEMATICA
nmax = 10^8; sppQ[n_?EvenQ, _] := False; sppQ[n_?PrimeQ, _] := False; sppQ[n_, b_] := (s = IntegerExponent[n - 1, 2]; d = (n - 1)/2^s; If[ PowerMod[b, d, n] == 1, Return[True], Do[ If[ PowerMod[b, d*2^r, n] == n-1, Return[True]], {r, 0, s-1}]]); A072276 = {}; n = 1; While[n < nmax, n = n+2; If[sppQ[n, 2] && sppQ[n, 3] , Print[n]; AppendTo[ A072276, n]]]; A072276 (* Jean-François Alcover, Oct 20 2011, after R. J. Mathar *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Francois R. Grieu, Jul 09 2002
STATUS
approved