A121022 Even numbers containing a 2 in their decimal representation.

2, 12, 20, 22, 24, 26, 28, 32, 42, 52, 62, 72, 82, 92, 102, 112, 120, 122, 124, 126, 128, 132, 142, 152, 162, 172, 182, 192, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246, 248, 250, 252

Offset: 1

Author

Reinhard Zumkeller, Jul 21 2006

Keywords

• nonn
• base
• easy

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Seong Ju Kim, R. Stees, L. Taalman, Sequences of Spiral Knot Determinants, Journal of Integer Sequences, Vol. 19 (2016), # 16.1.4.
• Ryan Stees, Sequences of Spiral Knot Determinants, Senior Honors Projects, Paper 84, James Madison Univ., May 2016.
• Index entries for 10-automatic sequences.

Crossrefs

Intersection of A005843 and A011532.

Cf. A121041, A011531, A121023, A121024, A121025, A121026, A121027, A121028, A121029, A121030, A121031, A121032, A121033, A121034, A121035, A121036, A121037, A121038, A121039, A121040.

Programs

Haskell

a121022 n = a121022_list !! (n-1)
a121022_list = filter (('2' `elem`) . show) [0, 2 ..]
-- Reinhard Zumkeller, Nov 08 2013

Mathematica

Select[2*Range[200],DigitCount[#,10,2]>0&] (* Harvey P. Dale, Nov 04 2013 *)

PARI

is(n) = n%2==0 && setsearch(vecsort(digits(n)), 2) \\ Felix Fröhlich, Nov 22 2020

Formula

a(n) ~ 2n. - Charles R Greathouse IV, Mar 30 2022