A381074 Numbers k such that k, k+2 and k+4 are all terms in A380846.
10820236, 24069388, 27802288, 39297580, 50717488, 56362960, 73070224, 97339504, 103605964, 112209580, 112526032, 140053564, 145315600, 155790124, 156415084, 158877232, 184667248, 185979664, 188913004, 189225484, 189541936, 224435536, 281740396, 292406380, 314388112
Offset: 1
Links
- Amiram Eldar, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
f[n_] := Module[{h = DigitCount[n, 2, 1]}, DivisorSum[n, # &, DigitCount[#, 2, 1] == h &] == 2*n]; seq[lim_] := Module[{q = Table[False, {6}], s = {}}, q[[1 ;; 4]] = f /@ Range[4]; Do[q[[5 ;; 6]] = f /@ Range[k, k + 1]; If[q[[1]] && q[[3]] && q[[5]], AppendTo[s, k - 4]]; If[q[[2]] && q[[4]] && q[[6]], AppendTo[s, k - 3]]; q[[1 ;; 4]] = q[[3 ;; 6]], {k, 5, lim, 2}]; s]; seq[11000000] -
PARI
is1(k) = {my(h = hammingweight(k)); sumdiv(k, d, d*(hammingweight(d) == h)) == 2*k;} list(lim) = {my(q1 = is1(1), q2 = is1(2), q3 = is1(3), q4 = is1(4), q5, q6); forstep(k = 5, lim, 2, q5 = is1(k); q6 = is1(k+1); if(q1 && q3 && q5, print1(k-4, ", ")); if(q2 && q4 && q6, print1(k-3, ", ")); q1 = q3; q2 = q4; q3 = q5; q4 = q6);}
Comments