%I #34 Aug 30 2017 12:15:18

%S 1,4,9,16,25,72,49,104,81,160,121,348,143,322,285,352,221,648,323,800,

%T 567,814,437,1272,575,1066,729,1204,667,2370,713,1376,1221,1598,1225,

%U 2592,1073,2242,1833,2840,1271,4326,1333,2816,2565,2806,1457,4272,1813

%N a(1)=1. a(n) is the smallest positive multiple of n such that phi(a(n)) > phi(a(n-1)), where phi(m) is A000010(m).

%H Ivan Neretin and Peter Kagey, <a href="/A143480/b143480.txt">Table of n, a(n) for n = 1..10000</a>, first 1000 terms from Ivan Neretin.

%p n:= 1: A[1]:= 1:

%p p:= 1:

%p for n from 2 to 100 do

%p for k from ceil(p/n)*n by n do

%p r:= numtheory:-phi(k);

%p if r > p then

%p A[n]:= k;

%p p:= r;

%p break

%p fi

%p od:

%p od:

%p seq(A[i],i=1..100); # _Robert Israel_, Sep 04 2015

%t a = b = {1}; Do[k = 1; While[(r = EulerPhi[nxt = k*n]) <= b[[-1]], k++]; AppendTo[a, nxt]; AppendTo[b, r], {n, 2, 49}]; a (* _Ivan Neretin_, May 25 2015 *)

%t FoldList[Block[{e = EulerPhi@ #1, k = 1, m}, While[EulerPhi[Set[m, k #2]] <= e, k++]; m] &, Range@ 49] (* _Michael De Vlieger_, Aug 29 2017 *)

%Y Cf. A000010, A143481 (phi(a(n))), A143482 (similar, with >= rather than >), A259439 (a(n)/n).

%K nonn

%O 1,2

%A _Leroy Quet_, Aug 19 2008

%E Extended by _Ray Chandler_, Nov 09 2008