OFFSET
1,1
LINKS
Gareth A. Jones and Alexander K. Zvonkin, A number-theoretic problem concerning pseudo-real Riemann surfaces, arXiv:2401.00270 [math.NT], 2023. See Table 2 at page 7.
MATHEMATICA
a[n_] := Length[Join[{1}, Select[Range[10^n], PrimeQ[f = First/@FactorInteger[#]] == Table[True, {j, PrimeNu[#]}] && Mod[f, 4] == Table[1, {m, PrimeNu[#]}] && #<=10^n &]]]; Array[a, 9]
PROG
(PARI) is1(n) = n % 4 == 1 && factorback(factor(n)[, 1] % 4) == 1 \\ Charles R Greathouse IV at A004613
lista(nmax) = {my(c = 0, pow = 10, n = 1, nm = nmax + 1); for(k = 1, 10^nmax + 1, if(k > pow, print1(c, ", "); pow *= 10; n++; if(n == nm, break)); if(is1(k), c++)); } \\ Amiram Eldar, Jun 03 2024
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Stefano Spezia, Jan 13 2024
EXTENSIONS
a(10)-a(11) from Amiram Eldar, Jun 03 2024
STATUS
approved