A163074 Swinging primes: primes which are within 1 of a swinging factorial (A056040).
2, 3, 5, 7, 19, 29, 31, 71, 139, 251, 631, 3433, 12011, 48619, 51479, 51481, 2704157, 155117519, 280816201, 4808643121, 35345263801, 81676217699, 1378465288199, 2104098963721, 5651707681619, 94684453367401, 386971244197199, 1580132580471899, 1580132580471901
Offset: 1
Keywords
Examples
3$ + 1 = 7 is prime, so 7 is in the sequence. (Here '$' denotes the swinging factorial function.)
Links
- Jinyuan Wang, Table of n, a(n) for n = 1..103
- Peter Luschny, Die schwingende Fakultät und Orbitalsysteme, August 2011.
- Peter Luschny, Swinging Primes.
Programs
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Maple
# Seq with arguments <= n: a := proc(n) select(isprime,map(x -> A056040(x)+1,[$1..n])); select(isprime,map(x -> A056040(x)-1,[$1..n])); sort(convert(convert(%%,set) union convert(%,set),list)) end:
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Mathematica
Reap[Do[f = n!/Quotient[n, 2]!^2; If[PrimeQ[p = f - 1], Sow[p]]; If[PrimeQ[p = f + 1], Sow[p]], {n, 1, 45}]][[2, 1]] // Union (* Jean-François Alcover, Jun 28 2013 *)
Extensions
More terms from Jinyuan Wang, Mar 22 2020
Comments