The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A316561 Squarefree numbers whose arithmetic mean of digits is 4. 1
17, 26, 35, 53, 62, 71, 129, 138, 165, 174, 183, 219, 237, 246, 255, 273, 282, 291, 309, 318, 327, 345, 354, 381, 390, 417, 426, 435, 453, 462, 471, 534, 543, 561, 570, 606, 615, 633, 642, 651, 705, 714, 723, 741, 813, 822, 831, 903, 921, 930, 1069, 1087, 1159 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
26 = 2*13 is a 2-digit squarefree number whose arithmetic mean of digits is (2 + 6)/2 = 4. Hence, 26 is a term.
165 = 3 * 5 * 11 is a 3-digit squarefree number whose arithmetic mean of digits is (1 + 6 + 5)/3 = 4. Hence, 165 is a term.
MAPLE
filter:= proc(n) local L;
if not numtheory:-issqrfree(n) then return false fi;
L:= convert(n, base, 10);
convert(L, `+`)=4*nops(L)
end proc:
select(filter, [$1..1000]); # Robert Israel, Jul 06 2018
MATHEMATICA
Select[Range[5000], Mean[IntegerDigits[#]] == 4 && SquareFreeQ[#] &]
PROG
(Magma) [k:k in [4..1200]| IsSquarefree(k) and &+Intseq(k) eq 4*#Intseq(k)]: // Marius A. Burtea, Dec 19 2019
CROSSREFS
Intersection of A005117 (squarefree numbers) and A061387.
Cf. A316484.
Sequence in context: A212909 A273785 A171169 * A034963 A120143 A031204
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, Jul 06 2018
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 17 03:01 EDT 2024. Contains 373432 sequences. (Running on oeis4.)