The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A023651 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A023651

Numbers k such that (product of digits of k) * (sum of digits of k) = 2k.
(history; published version)

#18 by Michael De Vlieger at Mon Feb 26 09:19:05 EST 2024

STATUS

reviewed

approved

#17 by Joerg Arndt at Mon Feb 26 01:27:14 EST 2024

STATUS

proposed

reviewed

#16 by Jason Yuen at Mon Feb 26 00:39:17 EST 2024

STATUS

editing

proposed

#15 by Jason Yuen at Mon Feb 26 00:39:02 EST 2024

COMMENTS

Except for k = 0, this sequence is a subsequence of A049101. - Jason Yuen, Feb 26 2024

CROSSREFS

Cf. A007953, A007954, A049101.

KEYWORD

nonn,base,fini,morefull

STATUS

approved

editing

#14 by Peter Luschny at Sat Jul 23 03:24:53 EDT 2022

STATUS

reviewed

approved

#13 by Michel Marcus at Sat Jul 23 01:37:57 EDT 2022

STATUS

proposed

reviewed

#12 by Mohammed Yaseen at Fri Jul 22 12:50:29 EDT 2022

STATUS

editing

proposed

#11 by Mohammed Yaseen at Fri Jul 22 12:47:32 EDT 2022

PROG

if p(n)*s(n)==2*n:

print(n) # Mohammed Yaseen, Jul 22 2022

#10 by Mohammed Yaseen at Fri Jul 22 12:45:08 EDT 2022

NAME

Numbers k such that (product of digits of nk) * (sum of digits of nk) = 2n2k.

PROG

(PARI) isok(n) = if(n, factorback(digits(n)), 0) * sumdigits(n) == 2*n \\ Mohammed Yaseen, Jul 22 2022

(Python)

from math import prod

def s(n): return sum(map(int, str(n)))

def p(n): return prod(map(int, str(n)))

for n in range(0, 10**6):

if p(n)*s(n)==2*n:

print(n) # Mohammed Yaseen, Jul 22 2022

CROSSREFS

2n = A007953(n) * A007954(n). Cf. A038369.

Cf. A007953, A007954.

Cf. A038364, A038369, A062237, A066282.

KEYWORD

nonn,base,fini,more

STATUS

approved

editing

#9 by N. J. A. Sloane at Fri Dec 15 17:34:47 EST 2017

AUTHOR

_Jason Earls (zevi_35711(AT)yahoo.com), _, Dec 11 2001

Discussion

Fri Dec 15

17:34

OEIS Server: https://oeis.org/edit/global/2722