A202237 Odd numbers with the same number of prime factors of the form 4*k+1 and 4*k+3.

1, 15, 35, 39, 51, 55, 87, 91, 95, 111, 115, 119, 123, 143, 155, 159, 183, 187, 203, 215, 219, 225, 235, 247, 259, 267, 287, 291, 295, 299, 303, 319, 323, 327, 335, 339, 355, 371, 391, 395, 403, 407, 411, 415, 427, 447, 451, 471, 511, 515, 519, 525, 527, 535, 543, 551

Offset

1,2

Comments

Primes are counted with multiplicity.

Closed under multiplication.

Links

Table of n, a(n) for n=1..56.

Maple

isA202237 := proc(n)
    if type(n, 'odd') then
        A083025(n) = A065339(n) ;
    else
        false;
    end if;
end proc:
for n from 1 to 200 do
    if isA202237(n) then
        printf("%d, ", n);
    end if;
end do: # R. J. Mathar, Dec 16 2011

Mathematica

fQ[n_]:=Plus@@((Mod[#[[1]], 4]-2)*#[[2]]&/@If[==1, {}, FactorInteger[n]]==0 && OddQ[n]; Select[Range[600], fQ] (* Ray Chandler, Dec 20 2011 *)

Prog

(PARI) netprime(n)=local(fm=factor(n)); sum(k=1, matsize(fm)[1], if(fm[k, 1]==2, 0, if(fm[k, 1]%4==1, fm[k, 2], -fm[k, 2])))
ap(n)=forstep(k=1, n, 2, if(netprime(k)==0, print1(k", ")))

Crossrefs

A080774 (primitive elements), A072202 (even allowed).

Sequence in context: A360110 A359163 A327934 * A080774 A146319 A238605

Adjacent sequences: A202234 A202235 A202236 * A202238 A202239 A202240

Keyword

nonn

Author

Franklin T. Adams-Watters, Dec 16 2011

Status

approved