login
A143480
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).
5
1, 4, 9, 16, 25, 72, 49, 104, 81, 160, 121, 348, 143, 322, 285, 352, 221, 648, 323, 800, 567, 814, 437, 1272, 575, 1066, 729, 1204, 667, 2370, 713, 1376, 1221, 1598, 1225, 2592, 1073, 2242, 1833, 2840, 1271, 4326, 1333, 2816, 2565, 2806, 1457, 4272, 1813
OFFSET
1,2
LINKS
Ivan Neretin and Peter Kagey, Table of n, a(n) for n = 1..10000, first 1000 terms from Ivan Neretin.
MAPLE
n:= 1: A[1]:= 1:
p:= 1:
for n from 2 to 100 do
for k from ceil(p/n)*n by n do
r:= numtheory:-phi(k);
if r > p then
A[n]:= k;
p:= r;
break
fi
od:
od:
seq(A[i], i=1..100); # Robert Israel, Sep 04 2015
MATHEMATICA
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 *)
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 *)
CROSSREFS
Cf. A000010, A143481 (phi(a(n))), A143482 (similar, with >= rather than >), A259439 (a(n)/n).
Sequence in context: A374927 A299153 A133900 * A230365 A274963 A353387
KEYWORD
nonn
AUTHOR
Leroy Quet, Aug 19 2008
EXTENSIONS
Extended by Ray Chandler, Nov 09 2008
STATUS
approved