A100897 a(n) is the decimal expansion of 7nn7.

7007, 7117, 7227, 7337, 7447, 7557, 7667, 7777, 7887, 7997, 710107, 711117, 712127, 713137, 714147, 715157, 716167, 717177, 718187, 719197, 720207, 721217, 722227, 723237, 724247, 725257, 726267, 727277, 728287, 729297, 730307

Offset

0,1

Links

Daniel Starodubtsev, Table of n, a(n) for n = 0..10000

Formula

a(n) = 7nn7.

Example

If n=6, 7nn7 is 7667.
If n=15, 7nn7 is 715157 (a prime)
If n=18, 7nn7 is 718187 (a prime)
If n=19, 7nn7 is 719197 (a prime)

Maple

a:= n-> parse(cat(7, n, n, 7)):
seq(a(n), n=0..35);  # Alois P. Heinz, Jan 24 2020

Mathematica

Table[idn=IntegerDigits[n]; FromDigits[Join[{7}, idn, idn, {7}]], {n, 0, 30}] (* Harvey P. Dale, May 14 2013 *)

Crossrefs

Cf. A100846.

Sequence in context: A050663 A114615 A209879 * A206757 A236061 A317399

Adjacent sequences: A100894 A100895 A100896 * A100898 A100899 A100900

Keyword

nonn,base,easy

Author

Parthasarathy Nambi, Jan 10 2005

Status

approved