The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A324849 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A324849

Positive integers divisible by none of their prime indices > 1.
(history; published version)

#12 by Alois P. Heinz at Thu Mar 21 04:16:06 EDT 2019

STATUS

proposed

approved

#11 by Felix Fröhlich at Thu Mar 21 03:26:03 EDT 2019

STATUS

editing

proposed

#10 by Felix Fröhlich at Thu Mar 21 03:25:11 EDT 2019

PROG

(PARI) is(n) = my(f=factor(n)[, 1]~, idc=[]); for(k=1, #f, idc=concat(idc, [primepi(f[k])])); for(t=1, #idc, if(idc[t]==1, next); if(n%idc[t]==0, return(0))); 1 \\ Felix Fröhlich, Mar 21 2019

STATUS

proposed

editing

#9 by Robert Israel at Wed Mar 20 21:49:23 EDT 2019

STATUS

editing

proposed

#8 by Robert Israel at Wed Mar 20 21:49:07 EDT 2019

LINKS

Robert Israel, <a href="/A324849/b324849.txt">Table of n, a(n) for n = 1..10000</a>

MAPLE

filter:= proc(n) andmap(t -> not ((n/numtheory:-pi(t))::integer), numtheory:-factorset(n) minus {2}) end proc:

select(filter, [$1..200]); # Robert Israel, Mar 20 2019

STATUS

approved

editing

#7 by Susanna Cuyler at Tue Mar 19 07:16:00 EDT 2019

STATUS

proposed

approved

#6 by Gus Wiseman at Mon Mar 18 23:43:08 EDT 2019

STATUS

editing

proposed

#5 by Gus Wiseman at Mon Mar 18 23:42:50 EDT 2019

CROSSREFS

Cf. A324695, A324741, A324743, A324756, A324758, A324765, A324846, A324847, A324848, A324850, A324852, A324853, A324856.

#4 by Gus Wiseman at Mon Mar 18 22:46:01 EDT 2019

EXAMPLE

The sequence of terms together with their prime indices begins:

1: {}

2: {1}

3: {2}

4: {1,1}

5: {3}

7: {4}

8: {1,1,1}

9: {2,2}

10: {1,3}

11: {5}

13: {6}

14: {1,4}

16: {1,1,1,1}

17: {7}

19: {8}

20: {1,1,3}

21: {2,4}

22: {1,5}

23: {9}

25: {3,3}

CROSSREFS

Cf. A003963, A056239, A112798, A120383, A289509, A290822, A304360, A306844.

Cf. A324695, A324741, A324743, A324756, A324758, A324759, A324765, A324846, A324847, A324848, A324850, A324852, A324853.

#3 by Gus Wiseman at Mon Mar 18 22:43:02 EDT 2019

CROSSREFS

Cf. A324695, A324741, A324743, A324756, A324758, A324759, A324765, A324846, A324847, A324848, A324850, A324852, A324853.

Cf. A324846, A324847, A324848, A324850, A324852, A324853.