A067790 Numbers n such that n and prime(n) end with the same digit.

7, 11, 23, 29, 37, 103, 107, 109, 121, 141, 143, 149, 153, 169, 183, 187, 189, 209, 213, 217, 221, 239, 243, 247, 249, 271, 273, 277, 289, 291, 293, 299, 307, 309, 321, 331, 351, 367, 379, 381, 407, 413, 431, 449, 453, 469, 489, 497, 499, 501, 503, 513, 519

Offset

1,1

Comments

First composite term is 121, which corresponds to the prime 661. There are no multiples of 5 in the sequence. - Alonso del Arte, Jan 23 2020

Links

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

Robert Israel, Plot of (a(n)-10 n)/sqrt(n)

Formula

It seems that a(n) is asymptotic to 10n and that a(n) = 10n + O(sqrt(n)) (i.e. (a(n) - 10n)/sqrt(n) is bounded).

Example

prime(973) = 7673, hence 973 is in the sequence.

Maple

P:= select(isprime, [2, seq(i, i=3..10000, 2)]):
select(n -> (n - P[n]) mod 10 = 0, [$1..nops(P)]); # Robert Israel, May 17 2017

Mathematica

Select[Range[600], Mod[#, 10] == Mod[Prime[#], 10] &] (* Harvey P. Dale, Oct 18 2018 *)

Crossrefs

Cf. A085598, A271043.

Sequence in context: A033207 A095084 A182569 * A271043 A089056 A210981

Adjacent sequences: A067787 A067788 A067789 * A067791 A067792 A067793

Keyword

easy,nonn,base

Author

Benoit Cloitre, Mar 07 2002

Status

approved