A069204 Emirps congruent to their reversal mod 4.

37, 73, 149, 179, 199, 337, 347, 733, 743, 941, 971, 991, 1009, 1021, 1033, 1061, 1069, 1097, 1103, 1151, 1201, 1213, 1217, 1229, 1237, 1249, 1399, 1409, 1429, 1453, 1511, 1523, 1559, 1583, 1601, 1657, 1669, 1723, 1979, 3011, 3019, 3023, 3067, 3083

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10000

Example

179 and 971 are both congruent to 3 (mod 4); 337 and 733 are both congruent to 1 (mod 4).

Mathematica

f[n_] := ToExpression[ StringReverse[ ToString[n]]]; Select[ Range[4000], PrimeQ[f[ # ]] && PrimeQ[ # ] && f[ # ] != # && Mod[ #, 4] == Mod[f[ # ], 4] &];
okQ[n_]:=Module[{rn=FromDigits[Reverse[IntegerDigits[n]]]}, rn!=n&& PrimeQ[ rn] && Mod[n, 4]==Mod[rn, 4]]; Select[Prime[Range[500]], okQ] (* Harvey P. Dale, Dec 19 2010 *)

Prog

(Python)
from sympy import isprime
def ok(n): return isprime(n) and isprime(r:=int(str(n)[::-1])) and r!=n and n%4==r%4
print([k for k in range(3100) if ok(k)]) # Michael S. Branicky, Aug 12 2023

Crossrefs

Cf. A006567.

Sequence in context: A043243 A044023 A179579 * A153208 A128388 A137833

Adjacent sequences: A069201 A069202 A069203 * A069205 A069206 A069207

Keyword

base,nonn

Author

Lekraj Beedassy, Apr 11 2002

Extensions

More terms from Jason Earls and Robert G. Wilson v, Apr 14 2002

Offset corrected by Mohammed Yaseen, Aug 11 2023

Status

approved