A087025 - OEIS

%I #19 Jul 07 2023 21:22:22

%S 255360,17205180696931968,1951532915603927040,12430490030984319840000,

%T 9956179688423375044684800000,

%U 6080633705911286890368486450696472902951229440,4809378729404888733987843426081300724182624228548100710400

%N Sum of divisors of n-th cyclic number.

%C Calculated with Dario Alpern's ECM.

%C Extended using factors of 10^(A001913(n)-1)-1, see Kamada link.

%H Max Alekseyev, <a href="/A087025/b087025.txt">Table of n, a(n) for n = 1..51</a> (first 42 terms from Ray Chandler)

%H Dario A. Alpern, <a href="https://www.alpertron.com.ar/ECM.HTM">Factorization using the Elliptic Curve Method</a>.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/repunit/">Factorizations of 11...11 (Repunit)</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CyclicNumber.html">Cyclic Number</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DivisorFunction.html">Divisor Function</a>

%F a(n) = A000203(A004042(n+1)).

%Y Cf. A001913, A087020, A087021, A087022, A087023, A087024, A087026.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Jul 30 2003

%E a(12)-a(42) from _Ray Chandler_, Nov 16 2011