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 A328117 Numbers such that zero or more applications of A003415 (arithmetic derivative) will yield 7. 3
 7, 10, 18, 21, 25, 38, 46, 65, 77, 98, 129, 170, 205, 217, 254, 361, 414, 426, 462, 493, 501, 529, 718, 753, 982, 998, 1141, 1362, 1501, 1502, 2041, 2045, 2077, 2105, 2257, 2285, 2869, 2933, 2998, 3102, 3133, 3706, 4066, 4078, 4309, 4497, 4885, 5213, 5214, 5461, 5837, 6363, 6410, 6546, 6649, 6749, 6901, 6913, 6937, 6953, 7011 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Union of {7} with those terms of k of A099308 for which A327968(k) = 7. LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 EXAMPLE a(4) = 21 is included as A003415(A003415(21)) = 7. a(627664) = 4294966334 (= 2^32 - 962) is included as A003415^(14)(4294966334) = 7. Note that A327966(4294966334) = 16. PROG (PARI) A003415checked(n) = if(n<=1, 0, my(f=factor(n), s=0); for(i=1, #f~, if(f[i, 2]>=f[i, 1], return(0), s += f[i, 2]/f[i, 1])); (n*s)); isA328117(n) = { while((n>7), n = A003415checked(n)); (7==n); }; CROSSREFS Cf. A003415, A099308, A327966, A327968, A327977, A328115. Sequence in context: A098748 A020692 A124187 * A155027 A118420 A196939 Adjacent sequences:  A328114 A328115 A328116 * A328118 A328119 A328120 KEYWORD nonn AUTHOR Antti Karttunen, Oct 06 2019 STATUS approved

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Last modified August 12 17:17 EDT 2020. Contains 336439 sequences. (Running on oeis4.)