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A194578 Numbers n such that the sum of the first k divisors of n^2+1 is equal to n for some k. 0
1, 3, 43, 68, 93, 228, 612, 1903, 32292, 44868, 252072, 36564198, 55862807, 134735264 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
No further at least up to 10^7.
No other terms up to 10^8. - Michel Marcus, Jan 17 2014
a(15) > 2.5*10^8. - Giovanni Resta, Apr 14 2017
LINKS
EXAMPLE
The divisors of 43^2 + 1 are {1, 2, 5, 10, 25, 37, 50, 74, 185, 370, 925, 1850} and 1+2+5+10 + 25 = 43, hence 43 is in the list.
MATHEMATICA
Select[Range[10000000], MemberQ[Accumulate[Divisors[#^2+1]], #]&]
CROSSREFS
Cf. A185584.
Sequence in context: A337213 A059802 A139854 * A185632 A006033 A246994
KEYWORD
nonn
AUTHOR
Michel Lagneau, Aug 29 2011
EXTENSIONS
a(12)-a(13) from Michel Marcus, Jan 17 2014
a(14) from Giovanni Resta, Apr 14 2017
STATUS
approved

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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)