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 A279058 Least number k = concat(x,y) such that k = n*(x+y) - x * y , -1 if such a number does not exist. 2
 17, 13, 25, 11, 33, 55, 41, 10, 126, 224, 189, 268, 434, 106, 729, 1539, 981, 315, 1079, 313, 844, 416, 415, 1178551, 1373, 309, 1471, 1575, 721, 1456, 1667, 1133, 820, 306, 818, 612, 1961, 305, 2059, 1224, 406, 1530, 2255, 1527, 2353, 2142, 1217, 1420, 101, 303 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 COMMENTS a(10^k) = 10^k, for k>=1. MSD of y can be 0. In the first 1000 terms only 30060 is present two times, in a(354) and a(480). LINKS Paolo P. Lava, Table of n, a(n) for n = 3..1000 EXAMPLE a(11) = 126 = concat(12,6) and 11*(12 + 6) - 12*6 = 126; a(222) =  3921381 = concat(39,21381) and 222*(39 + 21381) - 39*21381 = 3921381. MAPLE with(numtheory): P:=proc(q) local j, k, s, t, n, ok; for j from 3 to q do ok:=1; for n from 1 to q do if ok=0 then break; else for k from 1 to ilog10(n) do s:=n mod 10^k; t:=trunc(n/10^k); if j*(s+t)-s*t=n then print(n); ok:=0; break; fi; od; fi; od; od; end: P(10^6); CROSSREFS Cf. A278935. Sequence in context: A063518 A168250 A089502 * A195534 A128158 A278824 Adjacent sequences:  A279055 A279056 A279057 * A279059 A279060 A279061 KEYWORD nonn,base AUTHOR Paolo P. Lava, Dec 05 2016 EXTENSIONS a(258) by Giovanni Resta, Dec 05 2016 STATUS approved

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Last modified January 17 05:26 EST 2019. Contains 319207 sequences. (Running on oeis4.)