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A369953
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a(n) is the least integer k such that the sum of the digits of k^2 is 9*n.
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3
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0, 3, 24, 63, 264, 1374, 3114, 8937, 60663, 94863, 545793, 1989417, 5477133, 20736417, 82395387, 260191833, 706399164, 2428989417, 9380293167, 28105157886, 99497231067, 538479339417, 1974763271886, 4472135831667, 14106593458167, 62441868958167, 244744764757083, 836594274358167
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OFFSET
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0,2
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COMMENTS
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3|a(n).
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LINKS
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FORMULA
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EXAMPLE
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a(3)=63 because k=63 is the least integer k such that the sum of the digits of k^2 = 3969 is 9*3 = 27 (3+9+6+9 = 27).
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MATHEMATICA
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n=1; lst={}; For[k=0, k<10^8, k+=3, If[Total[IntegerDigits[k^2]]==9*n, AppendTo[lst, k]; n++]]; lst
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PROG
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(Python)
n=1
lst=[]
for k in range(0, 10**8, 3):
if sum(int(d) for d in str(k*k))==9*n:
lst.append(k)
n=n+1
print(lst)
(PARI) a(n) = my(k=0); while(sumdigits(k^2) != 9*n, k+=3); k; \\ Michel Marcus, Feb 17 2024
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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