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 A269309 Consider the Euler totient function of a number x. Take the sum of its digits. Repeat the process deleting the first addendum and adding the previous sum. The sequence lists the numbers that after some iterations reach x. 6
 13, 21, 63, 177, 206, 412, 655, 824, 1990, 2637, 11438, 12485, 23846, 34132, 40528, 56202, 87539, 94597, 1288999, 3075239, 3106991, 20689503, 31173397, 46230492, 65889985, 79476719, 170859904, 266368503, 295845211, 420471958, 445169688, 797687940, 962257660 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..33. EXAMPLE phi(13) = 12 : 1 + 2 = 3; 2 + 3 = 5; 3 + 5 = 8; 5 + 8 = 13. MAPLE with(numtheory): P:=proc(q, h) local a, b, k, n, t, v; v:=array(1..h); for n from 2 to q do a:=phi(n); b:=ilog10(a)+1; if b>1 then for k from 1 to b do v[b-k+1]:=(a mod 10); a:=trunc(a/10); od; t:=b+1; v[t]:=add(v[k], k=1..b); while v[t]= 10 && (d = IntegerDigits[EulerPhi[#]]; While[Total[d] < #, d = Join[Rest[d], {Total[d]}]; ]; Total[d] == #) &] (* Robert Price, May 21 2019 *) CROSSREFS Cf. A000010, A007629, A269307, A269308, A269310, A269311, A269312. Sequence in context: A275243 A066630 A147435 * A203854 A325448 A056523 Adjacent sequences: A269306 A269307 A269308 * A269310 A269311 A269312 KEYWORD nonn,base AUTHOR Paolo P. Lava, Feb 24 2016 EXTENSIONS a(19)-a(33) from Lars Blomberg, Jan 18 2018 STATUS approved

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Last modified December 4 01:17 EST 2023. Contains 367541 sequences. (Running on oeis4.)