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A097752 Least integer with each "mod 4 prime signature". 8
1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 21, 24, 25, 27, 30, 32, 36, 40, 42, 45, 48, 50, 54, 60, 63, 64, 65, 72, 75, 80, 81, 84, 90, 96, 100, 105, 108, 120, 125, 126, 128, 130, 135, 144, 150, 160, 162, 168, 180, 189, 192, 195, 200, 210, 216, 225, 231, 240, 243 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
See A097751 for definition of "mod 4 prime signature".
A097751 sorted and duplicates removed; n such that A097751(n)=n.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
MATHEMATICA
mod4PrimeSignature[n_] := {fi = FactorInteger[n]; If[OddQ[n], 0, fi[[1, 2]]], Select[fi, Mod[#[[1]], 4] == 3 &][[All, 2]]//Sort, Select[fi, Mod[#[[1]], 4] == 1 &][[All, 2]]}; A097751[n_] := Catch[For[k = 2, True, k++, If[ mod4PrimeSignature[k] == mod4PrimeSignature[n], Throw[k]]]]; A097751[1] = 1; Select[ Range[243], A097751[#] == # &] (* Jean-François Alcover, Jan 10 2013 *)
PROG
(PARI) is(n)=n>>=valuation(n, 2); my(e3=valuation(n, 3), e1=valuation(n, 5), e); n/=3^e3 * 5^e1; forprime(p=7, , e=valuation(n, p); if(p%4==1, if(e1<e, return(0)); e1=e, if(e3<e, return(0)); e3=e); if(e, n/=p^e, if(e1==0 && e3==0, return(n==1)))) \\ Charles R Greathouse IV, Dec 10 2016
(PARI) See Greathouse link.
CROSSREFS
Sequence in context: A010432 A187041 A364560 * A014866 A051661 A051037
KEYWORD
nonn
AUTHOR
Ray Chandler, Aug 26 2004
STATUS
approved

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Last modified May 29 08:50 EDT 2024. Contains 372926 sequences. (Running on oeis4.)