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 A090088 Smallest even pseudoprimes to odd base=2n-1, not necessarily exceeding n. See also A007535 and A090086, A090087. 4
 4, 286, 4, 6, 4, 10, 4, 14, 4, 6, 4, 22, 4, 26, 4, 6, 4, 34, 4, 38, 4, 6, 4, 46, 4, 10, 4, 6, 4, 58, 4, 62, 4, 6, 4, 10, 4, 74, 4, 6, 4, 82, 4, 86, 4, 6, 4, 94, 4, 14, 4, 6, 4, 106, 4, 10, 4, 6, 4, 118, 4, 122, 4, 6, 4, 10, 4, 134, 4, 6, 4, 142, 4, 146, 4, 6, 4, 14, 4, 158, 4, 6, 4, 166, 4, 10 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For an even base there are no even pseudoprimes. LINKS Antti Karttunen, Table of n, a(n) for n = 1..16520 Antti Karttunen, Data supplement: n, a(n) computed for n =  1..100000 FORMULA a(n) = Min_{x=even number; (-1 + n^(x-1)) mod x = 0}. EXAMPLE n=2, 2n-2=3 as base, smallest relevant power is -1+2^(286-1) which is divisible by 286. MATHEMATICA Array[Block[{k = 4}, While[PowerMod[2 # - 1, k - 1, k] != 1, k += 2]; k] &, 86] (* Michael De Vlieger, Nov 13 2018 *) PROG (PARI) A090088(n) = { forstep(k=4, oo, 2, if(1==(Mod(n+n-1, k)^(k-1)), return (k)); ); } \\ (After code in A090086) - Antti Karttunen, Nov 10 2018 CROSSREFS Cf. A007535, A090986, A090987, A090089. Sequence in context: A074309 A113256 A259495 * A253233 A242997 A221135 Adjacent sequences: A090085 A090086 A090087 * A090089 A090090 A090091 KEYWORD nonn AUTHOR Labos Elemer, Nov 25 2003 STATUS approved

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Last modified September 9 04:58 EDT 2024. Contains 375759 sequences. (Running on oeis4.)