A108119 Numbers k such that prime(k) and prime(k+1) are congruent to 1 (mod 10).

42, 53, 82, 115, 125, 141, 172, 177, 193, 233, 279, 369, 399, 431, 474, 500, 575, 580, 585, 650, 651, 672, 708, 737, 751, 760, 795, 798, 820, 841, 842, 863, 873, 933, 1019, 1031, 1099, 1112, 1166, 1178, 1225, 1245, 1266, 1312, 1352, 1436, 1463, 1479, 1505

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

A330366(n) = prime(a(n)). - Robert Israel, Apr 06 2026

Example

Prime(42)=181, prime(43)=191. This is the first pair of successive primes both ending with 1.

Maple

R:= NULL: p:= 2: count:= 0:
for k from 1 do
  q:= p; p:= nextprime(p);
  if q mod 10 = 1 and p mod 10 = 1 then
    count:= count+1; R:= R, k; if count = 100 then break fi
  fi
od:
R; # Robert Israel, Apr 06 2026

Mathematica

ra=Range[2000]; cnd=Mod[Prime[ # ], 10]==Mod[Prime[ #+1], 10]==1&; se=Select[ra, cnd]

Crossrefs

Cf. A330366.

Sequence in context: A186456 A181647 A105346 * A175103 A116262 A156394

Adjacent sequences: A108116 A108117 A108118 * A108120 A108121 A108122

Keyword

nonn

Author

Zak Seidov, Jun 04 2005

Status

approved