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A154528
Composites k such that (smallest digit of k) + (multiplicity of smallest digit of k) is an even composite.
1
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
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
KEYWORD
nonn,base
AUTHOR
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