A237437 Least prime p > prime(n+1) such that p is not a square mod the first n odd primes 3, 5, 7, 11, ..., prime(n+1).
5, 17, 17, 17, 83, 167, 167, 227, 2273, 5297, 5297, 69467, 69467, 116387, 348563, 348563, 2004917, 5472953, 8062073, 8062073
Offset: 1
Keywords
Examples
Let f(p) = list of Legendre (p|q) for q = 3, 5, 7, 11, 13, 17, 19, 23, ... Then f(p) is p=3: 0, -1, -1, 1, 1, -1, -1, 1, ... p=5: -1, 0, -1, 1, -1, -1, 1, -1, ... p=7: 1, -1, 0, -1, -1, -1, 1, -1, ... p=11: -1, 1, 1, 0, -1, -1, 1, -1, ... p=13: 1, -1, -1, -1, 0, 1, -1, 1, ... p=17: -1, -1, -1, -1, 1, 0, 1, -1, ... p=19: 1, 1, -1, -1, -1, 1, 0, -1, ... f(5) is the first list that begins with -1, so a(1) = 5. f(17) is the first list that begins with -1, -1, so a(2) = 17.
Links
- Wipawee Tangjai, Kodchaphon Wanichang, Montathip Srikao, and Punyanuch Kheawkrai, A Congruent Property of Gibonacci Number Modulo Prime, Int'l. J. Analysis Appl. (2023), Vol. 21, No. 24.
- Wikipedia, Legendre symbol
- Wikipedia, Quadratic residue
Crossrefs
Cf. A237436.
Programs
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Mathematica
Table[p = Prime[n + 2]; While[Length[Select[Prime[Range[2, n + 1]], JacobiSymbol[p, #] == -1 &]] < n, p = NextPrime[p]]; p, {n, 1, 20}]
Formula
a(n) = a(n+1) if and only if Legendre (a(n)|prime(n+2)) = -1.
Comments