A154528 Composites k such that (smallest digit of k) + (multiplicity of smallest digit of k) is an even composite.

9, 22, 34, 35, 36, 38, 39, 44, 56, 57, 58, 63, 65, 66, 75, 78, 85, 87, 88, 93, 95, 111, 224, 225, 226, 228, 232, 242, 252, 262, 272, 282, 292, 322, 333, 344, 345, 346, 348, 354, 355, 356, 357, 358, 364, 365, 366, 368, 369, 374, 375, 376, 377, 378, 384, 385, 386

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

9 (composite) is a term because 9 + 1 = 10 (even composite);
22 (composite) is a term because 2 + 2 = 4 (even composite);
34 (composite) is a term because 3 + 1 = 4 (even composite).

Maple

frequdig := proc(n, dig) local f, d ; f := 0 ; for d in convert(n, base, 10) do if d = dig then f :=f+1; end if; end do; f ; end proc:
A054054 := proc(n) min(op(convert(n, base, 10)) ) ; end proc:
for n from 1 to 500 do c := A002808(n) ; sdg := A054054(c) ; a := sdg +frequdig(c, sdg) ; if type(a, 'even') and not isprime(a) then printf("%d, ", c ) ; end if; end do: # R. J. Mathar, May 05 2010

Mathematica

ecQ[n_]:=Module[{idn=IntegerDigits[n], s, c}, s=Min[idn]; c=s+Count[idn, s]; EvenQ[c]&&AllTrue[ {n, c}, CompositeQ]]; Select[Range[400], ecQ] (* Harvey P. Dale, Jul 19 2023 *)

Crossrefs

Cf. A002808.

Sequence in context: A228009 A330477 A295008 * A130861 A049730 A131895

Adjacent sequences: A154525 A154526 A154527 * A154529 A154530 A154531

Keyword

nonn,base

Author

Juri-Stepan Gerasimov, Jan 11 2009

Extensions

Corrected (28 replaced with 38, 269 with 369) by R. J. Mathar, May 05 2010

Name and Example section edited by Jon E. Schoenfield, Feb 11 2019

Status

approved