A176172 3rd prime-factor of n-th product of 4 distinct primes.
5, 5, 5, 7, 5, 7, 5, 5, 7, 7, 7, 11, 5, 7, 5, 7, 5, 11, 7, 7, 7, 5, 11, 5, 7, 13, 7, 7, 5, 11, 13, 11, 7, 5, 7, 7, 5, 7, 13, 7, 5, 11, 11, 17, 7, 7, 11, 5, 7, 11, 11, 5, 11, 7, 5, 13, 7, 13, 17, 5, 7, 13, 11, 13, 7, 5, 11, 7, 7, 11, 19, 5, 11, 11, 7, 11, 7, 13, 5, 11, 17, 7, 13, 11, 7, 5, 7, 7, 5
Offset: 1
Keywords
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
N:= 10000: # to use products <= N Primes:= select(isprime, [2,seq(i,i=3..N/30)]): P4:= NULL: for ia from 1 to nops(Primes) do a:= Primes[ia]; for ib from 1 to ia-1 do b:= Primes[ib]; if 6*a*b > N then break fi; for ic from 1 to ib-1 do c:= Primes[ic]; if 2*a*b*c > N then break fi; for id from 1 to ic-1 do d:= Primes[id]; if a*b*c*d > N then break fi; R[a*b*c*d]:= b; P4:= P4, a*b*c*d; od od od od: P4:= sort([P4]): map(t -> R[t], P4); # Robert Israel, May 14 2019 -
Mathematica
f0[n_]:=Last/@FactorInteger[n]=={1,1,1,1};f1[n_]:=Min[First/@FactorInteger[n]];f2[n_]:=First/@FactorInteger[n][[2,1]];f3[n_]:=First/@FactorInteger[n][[3,1]];f4[n_]:=Max[First/@FactorInteger[n]];lst={};Do[If[f0[n],AppendTo[lst,f3[n]]],{n,0,2*7!}];lst
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