A328117 Numbers such that zero or more applications of A003415 (arithmetic derivative) will yield 7.

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

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

Antti Karttunen, Terms computed up to a(627664) = 4294966334; (all terms in range 1 .. 2^32)

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