

A099309


Numbers n whose kth arithmetic derivative is nonzero for all k. Complement of A099308.


13



4, 8, 12, 15, 16, 20, 24, 26, 27, 28, 32, 35, 36, 39, 40, 44, 45, 48, 50, 51, 52, 54, 55, 56, 60, 63, 64, 68, 69, 72, 74, 75, 76, 80, 81, 84, 86, 87, 88, 90, 91, 92, 95, 96, 99, 100, 102, 104, 106, 108, 110, 111, 112, 115, 116, 117, 119, 120, 122, 123, 124, 125, 128, 132
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OFFSET

1,1


COMMENTS

Numbers of the form n = m*p^p (where p is prime), i.e., multiples of some term in A051674, have n' = (m + m')*p^p, which is again of the same form, but strictly larger iff m > 1. Therefore successive derivatives grow to infinity in this case, and they are constant when m = 1. There are other terms in this sequence, but I conjecture that they all eventually lead to a term of this form, e.g., 26 > 15 > 8 etc.  M. F. Hasler, Apr 09 2015


REFERENCES

See A003415.


LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000


PROG

(PARI) is(n)=until(4>n=factorback(n~)*sum(i=1, #n, n[2, i]/n[1, i]), for(i=1, #n=factor(n)~, n[1, i]>n[2, i]return(1))) \\ M. F. Hasler, Apr 09 2015


CROSSREFS

Cf. A003415 (arithmetic derivative of n), A099307 (least k such that the kth arithmetic derivative of n is zero), A099308 (numbers whose kth arithmetic derivative is zero for some k).
Sequence in context: A248159 A190679 A009023 * A327929 A327864 A235865
Adjacent sequences: A099306 A099307 A099308 * A099310 A099311 A099312


KEYWORD

nonn


AUTHOR

T. D. Noe, Oct 12 2004


STATUS

approved



