login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A309883 Numbers k such that A003132(k^2) = A003132(k), where A003132(n) is the sum of the squares of the digits of n. 1
0, 1, 10, 35, 100, 152, 350, 377, 452, 539, 709, 1000, 1299, 1398, 1439, 1519, 1520, 1569, 1591, 1679, 1965, 2599, 2838, 3332, 3500, 3598, 3770, 4520, 4586, 4754, 4854, 5390, 5501, 5835, 5857, 6388, 6595, 6735, 6861, 6951, 7090, 7349, 7887, 8395, 9795, 10000, 10056, 10159, 10389, 11055, 11091, 12990, 12999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

If k is in the sequence, then so are k*10^r, r >= 1.

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

377^2 = 142129, A003132(377) = 3^2 + 7^2 + 7^2 = 107, A003132(142129) = 1^2 + 4^2 + 2^2 + 1^2 + 2^2 + 9^2 = 107.

MATHEMATICA

digSum[n_] := Total[IntegerDigits[n]^2]; Select[Range[0, 13000], digSum[#] == digSum[#^2] &] (* Amiram Eldar, Aug 22 2019 *)

PROG

(PARI) for(i = 0, 30000, if(norml2(digits(i^2)) == norml2(digits(i)), print1(i, ", ")))

(Python)

def A003132(n):

    s = 0

    while n > 0:

        s, n = s+(n%10)**2, n//10

    return s

n, a = 0, 0

while n < 50:

    if A003132(a) == A003132(a*a):

        n = n+1

        print(n, a)

    a = a+1 # A.H.M. Smeets, Aug 23 2019

(MAGMA) [0] cat [k:k in [1..13000]| &+[c^2: c in Intseq(k)] eq &+[c^2: c in Intseq(k^2)]]; // Marius A. Burtea, Aug 24 2019

CROSSREFS

Cf. A003132, A058369, A070276, A174460, A176670, A178213, A307735, A309884.

Sequence in context: A000447 A052472 A272352 * A049736 A048507 A240267

Adjacent sequences:  A309880 A309881 A309882 * A309884 A309885 A309886

KEYWORD

nonn,base

AUTHOR

Antonio Roldán, Aug 21 2019

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 10:45 EST 2019. Contains 329751 sequences. (Running on oeis4.)