A152819 "Upper primes" (see A152754).
2, 11, 37, 41, 43, 47, 59, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 227, 229, 233, 239, 251, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727
Offset: 1
Keywords
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..2490
Crossrefs
Cf. A152754.
Programs
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Mathematica
fh[n_,h_] := If[h==1, Mod[n,2], If[Mod[n,4]>=2,1,0]]; half[n_, h_ ] := Module[{t=1, s=0, m=n}, While[m>0, s += fh[m,h]*t; m=Quotient[m,4]; t *= 2]; s]; mb[n_] := FromDigits[Riffle[IntegerDigits[n, 2], 0], 2]; aQ[n_] := PrimeQ[n] && mb[half[ n,1]] < mb[half[n, 2]]; Select[Range[730], aQ] (* Amiram Eldar, Dec 16 2018 from the PARI code *) -
PARI
a000695(n) = fromdigits(binary(n), 4); half1(n) = { my(t=1, s=0); while(n>0, s += (n%2)*t; n \= 4; t *= 2); (s); }; \\ A059905 half2(n) = { my(t=1, s=0); while(n>0, s += ((n%4)>=2)*t; n \= 4; t *= 2); (s); }; \\ A059906 isok(n) = isprime(n) && a000695(half1(n)) < a000695(half2(n)); \\ Michel Marcus, Dec 15 2018
Extensions
More terms from Michel Marcus, Dec 15 2018
Comments