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 A348054 Positive integers that are the product of two integers ending with 7. 6
 49, 119, 189, 259, 289, 329, 399, 459, 469, 539, 609, 629, 679, 729, 749, 799, 819, 889, 959, 969, 999, 1029, 1099, 1139, 1169, 1239, 1269, 1309, 1369, 1379, 1449, 1479, 1519, 1539, 1589, 1649, 1659, 1729, 1739, 1799, 1809, 1819, 1869, 1939, 1989, 2009, 2079, 2109 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..48. FORMULA Lim_{n->infinity} a(n)/a(n-1) = 1. EXAMPLE 49 = 7*7, 119 = 7*17, 189 = 7*27, 259 = 7*37, 289 = 17*17, 329 = 7*47, 399 = 7*57, ... MATHEMATICA a={}; For[n=0, n<=210, n++, For[k=0, k<=n, k++, If[Mod[10*n+9, 10*k+7]==0 && Mod[(10*n+9)/(10*k+7), 10]==7 && 10*n+9>Max[a], AppendTo[a, 10*n+9]]]]; a PROG (Python) def aupto(lim): return sorted(set(a*b for a in range(7, lim//7+1, 10) for b in range(a, lim//a+1, 10))) print(aupto(2110)) # Michael S. Branicky, Sep 26 2021 CROSSREFS Cf. A017377 (supersequence), A053742 (ending with 5), A139245 (ending with 2), A324297 (ending with 6), A346950 (ending with 3), A347253 (ending with 4), A348055. Sequence in context: A044236 A044617 A216169 * A090095 A163245 A084733 Adjacent sequences: A348051 A348052 A348053 * A348055 A348056 A348057 KEYWORD nonn,base AUTHOR Stefano Spezia, Sep 26 2021 STATUS approved

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Last modified July 15 12:56 EDT 2024. Contains 374332 sequences. (Running on oeis4.)