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A135027 Numbers k such that the sum of the digits of k^2 is 10. Multiples of 10 are omitted. 3

%I #22 May 30 2021 22:05:42

%S 8,19,35,46,55,71,145,152,179,251,332,361,449,451,548,649,4499,20249,

%T 20251,24499,100549,114499,316261

%N Numbers k such that the sum of the digits of k^2 is 10. Multiples of 10 are omitted.

%C A subsequence of A056020. - _R. J. Mathar_, Feb 10 2008

%C Next term > 10000000. - _R. J. Mathar_, Oct 20 2009

%C If it exists, a(24) > 10^10. - _Hugo Pfoertner_, May 17 2021

%C If it exists, a(24) > 10^29. - _Michael S. Branicky_, May 30 2021

%H Michael S. Branicky, <a href="/A135027/a135027.txt">Python program</a>

%e Corresponding squares are 64, 361, 1225, 2116, 3025, 5041, 21025, 23104, 32041, 63001, 110224, 130321, 201601, 203401, 300304, 421201, 20241001, 410022001, 410103001, 600201001, 10110101401, 13110021001, 100021020121.

%e 8^2 = 64 and 6+4 = 10. 316261^2 = 100021020121 and 1+0+0+0+2+1+0+2+0+1+2+1 = 10. - _Zak Seidov_, Aug 26 2009

%t s={};Do[If[Mod[n,10]>0&&10==Total[IntegerDigits[n^2]],AppendTo[s,n]], {n,10^8}];s (* _Zak Seidov_, Aug 26 2009 *)

%o (Python)

%o def A007953(n):

%o a=0

%o sh=n

%o while sh > 0:

%o a += sh % 10

%o sh //= 10

%o return a

%o def isA135027(n):

%o if n % 10 == 0:

%o return False

%o else:

%o return A007953(n**2) == 10

%o for n in range(70000):

%o if isA135027(n):

%o print(n)

%o # _R. J. Mathar_, Oct 20 2009

%o (Python) # See linked program to go to large numbers

%o def ok(n): return n%10 != 0 and sum(map(int, str(n*n))) == 10

%o print(list(filter(ok, range(316262)))) # _Michael S. Branicky_, May 30 2021

%o (PARI) is(n) = sumdigits(n^2)==10 && n%10 > 0 \\ _Felix Fröhlich_, May 17 2021

%Y Cf. A007953, A056020.

%K base,more,nonn

%O 1,1

%A _Zak Seidov_, Feb 10 2008

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)