A082811 Smallest multiple of n beginning with 2.

2, 2, 21, 20, 20, 24, 21, 24, 27, 20, 22, 24, 26, 28, 210, 208, 204, 216, 209, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 210, 217, 224, 231, 204, 210, 216, 222, 228, 234, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 200, 204, 208, 212, 216, 220

Offset: 1

Author

Amarnath Murthy, Apr 19 2003

Keywords

• base
• easy
• nonn

Comments

a(n) is in {n, 2n, 3n, 4n, 5n, 6n, 7n, 11n, 12n, 13n, 14n}. [Charles R Greathouse IV, Mar 06 2011]

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A082784, A054850, A082786, A082787, A082788, A082789, A082791.

Cf. A000030.

Programs

Haskell

a082811 n = until ((== 2) . a000030) (+ n) n
-- Reinhard Zumkeller, Mar 27 2012

Mathematica

f[n_] := Block[{m = n}, While[ First@ IntegerDigits@ m != 2, m += n]; m]; Array[f, 55] (* Robert G. Wilson v *)

PARI

a(n)=forstep(k=n, 14*n, n, if(Vec(Str(k))[1]=="2", return(k))) \\ Charles R Greathouse IV, Mar 06 2011

Sage

def A082811(n): return next(k for k in PositiveIntegers() if (n*k).digits()[-1] == 2) # D. S. McNeil, Mar 07 2011