A122564 -id:A122564 - cp's OEIS frontend

A123079 Twin primes of form 4k+1.

5, 13, 17, 29, 41, 61, 73, 101, 109, 137, 149, 181, 193, 197, 229, 241, 269, 281, 313, 349, 421, 433, 461, 521, 569, 601, 617, 641, 661, 809, 821, 829, 857, 881, 1021, 1033, 1049, 1061, 1093, 1153, 1229, 1277, 1289, 1301, 1321, 1429, 1453, 1481, 1489, 1609

Offset: 1

Miklos Kristof, Sep 27 2006

nonn

Cf. A122564, A122565, A001097.

a[1]:=5:i:=2:for k from 6 to 3000 do if isprime(k) and isprime(k+2) then b:=k:c:=k+2: if b mod 4 = 1 then a[i]:=b:i:=i+1 fi: if c mod 4 = 1 then a[i]:=c:i:=i+1 fi:fi od: seq(a[n],n=1..i-1);

Select[Union[Flatten[Select[Partition[Prime[Range[300]],2,1],#[[2]]-#[[1]]==2&]]],Mod[ #,4]==1&] (* Harvey P. Dale, Oct 16 2022 *)

A123080 Twin primes of form 4k+3.

Original entry on oeis.org

3, 7, 11, 19, 31, 43, 59, 71, 103, 107, 139, 151, 179, 191, 199, 227, 239, 271, 283, 311, 347, 419, 431, 463, 523, 571, 599, 619, 643, 659, 811, 823, 827, 859, 883, 1019, 1031, 1051, 1063, 1091, 1151, 1231, 1279, 1291, 1303, 1319, 1427, 1451, 1483, 1487, 1607

Offset: 1

Miklos Kristof, Sep 27 2006

nonn

Cf. A122564, A122565, A001097.

i:=1:for k from 1 to 3000 do if isprime(k) and isprime(k+2) then b:=k:c:=k+2: if b mod 4 = 3 then a[i]:=b:i:=i+1 fi: if c mod 4 = 3 then a[i]:=c:i:=i+1 fi:fi od: seq(a[n],n=1..i-1);

Select[Flatten[Select[Partition[Prime[Range[260]],2,1],Last[#]-First[#] == 2&]], IntegerQ[(#-3)/4]&]  (* Harvey P. Dale, Apr 20 2011 *)

cp's OEIS Frontend

A123079 Twin primes of form 4k+1.

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