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 A280635 Numbers whose digit string can be partitioned into three nonempty parts such that the product of the first two parts equals the third part. 4
 111, 122, 133, 144, 155, 166, 177, 188, 199, 212, 224, 236, 248, 313, 326, 339, 414, 428, 515, 616, 717, 818, 919, 2510, 2612, 2714, 2816, 2918, 3412, 3515, 3618, 3721, 3824, 3927, 4312, 4416, 4520, 4624, 4728, 4832, 4936, 5210, 5315, 5420, 5525, 5630, 5735 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Could be called "area numbers" since if the first set of digits is the length, and the second set of digits is the width, then the last set of digits is the area, with length * width = area. LINKS EXAMPLE 236 is in the sequence since 2*3=6. 3515 is in the sequence since 3*5=15. Leading zeros are not allowed, thus 2036 (2*03=6) is not included. MAPLE read("transforms") : # implements digcatL isA280635 := proc(n)     local dgs, spl1, spl2, dgs1, dgs2, dgs3;     dgs := convert(n, base, 10) ;     if nops(dgs) >= 3 then         for spl1 from 1 to nops(dgs)-2 do         for spl2 from spl1+1 to nops(dgs)-1 do             if op(-1, dgs) <> 0 and op(spl1, dgs) <> 0 and op(spl2, dgs) <> 0 then                 dgs1 := ListTools[Reverse]([op(spl2+1..nops(dgs), dgs)]) ;                 dgs2 := ListTools[Reverse]([op(spl1+1..spl2, dgs)]) ;                 dgs3 := ListTools[Reverse]([op(1..spl1, dgs)]) ;                 if digcatL(dgs1)*digcatL(dgs2) = digcatL(dgs3) then                     return true;                 end if             end if;         end do:         end do:         false ;     else         false;     end if; end proc: for n from 100 do     if isA280635(n) then         printf("%d, \n", n) ;     end if; end do: # R. J. Mathar, Jan 10 2017 MATHEMATICA With[{nn = 1}, Union@ Flatten@ Table[FromDigits@ Flatten@ Map[IntegerDigits, {n, k, n k}], {n, 10^nn - 1}, {k, 10^nn - 1}]] (* Michael De Vlieger, Jan 07 2017 *) CROSSREFS Cf. A088294, A280636. Sequence in context: A326109 A208260 A222724 * A280732 A280636 A039990 Adjacent sequences:  A280632 A280633 A280634 * A280636 A280637 A280638 KEYWORD nonn,base AUTHOR Randy L. Ekl, Jan 06 2017 STATUS approved

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Last modified September 23 21:27 EDT 2020. Contains 337315 sequences. (Running on oeis4.)