|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
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
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
EXTENSIONS
|
Corrected (28 replaced with 38, 269 with 369) by R. J. Mathar, May 05 2010
|
|
STATUS
|
approved
|
|
|
|