A366666
Sum of the divisors of 9^n+1.
Original entry on oeis.org
3, 18, 126, 1332, 10476, 109926, 816732, 8906760, 64570086, 706911048, 5357742012, 56496274632, 456919958880, 4661686010664, 35152280388792, 388532214509688, 2779530283277766, 30018958465575240, 230668806145962744, 2431533550553980488, 19410628990783168944
Offset: 0
a(2)=126 because 9^2+1 has divisors {1, 2, 41, 82}.
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a:=n->numtheory[sigma](9^n+1):
seq(a(n), n=0..100);
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DivisorSigma[1, 9^Range[0,20] + 1] (* Paul F. Marrero Romero, Nov 14 2023 *)
A366607
Sum of the divisors of 4^n+1.
Original entry on oeis.org
3, 6, 18, 84, 258, 1302, 4356, 20520, 65538, 351120, 1110276, 5048232, 17041416, 82623888, 284225796, 1494039792, 4301668356, 20788904016, 73234343952, 332019460560, 1103789883396, 5936210280000, 18679788287496, 84884999116320, 282937726148616
Offset: 0
a(3)=84 because 4^3+1 has divisors {1, 5, 13, 65}.
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a:=n->numtheory[sigma](4^n+1):
seq(a(n), n=0..100);
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DivisorSigma[1,4^Range[0,30]+1] (* Paolo Xausa, Oct 14 2023 *)
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from sympy import divisor_sigma
def A366607(n): return divisor_sigma((1<<(n<<1))+1) # Chai Wah Wu, Oct 14 2023
A366629
Sum of the divisors of 6^n+1.
Original entry on oeis.org
3, 8, 38, 256, 1298, 9792, 52136, 338580, 1778436, 11889152, 62367272, 414625216, 2178461956, 15224775552, 80673299432, 611106029568, 2830769440776, 19344856702976, 115255634181184, 696800841097536, 3748220725527432, 27388329197137920, 135183433256806480
Offset: 0
a(3)=256 because 6^3+1 has divisors {1, 7, 31, 217}.
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a:=n->numtheory[sigma](6^n+1):
seq(a(n), n=0..100);
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DivisorSigma[1, 6^Range[0, 30] + 1] (* Paolo Xausa, Jul 03 2024 *)
A366638
Sum of the divisors of 7^n+1.
Original entry on oeis.org
3, 15, 93, 660, 3606, 34560, 236964, 1559520, 9155916, 77423280, 530807472, 3868683120, 21224771760, 185094572580, 1261494915594, 9988783073280, 49990612274316, 436182213726030, 3279858902194056, 21372989348391720, 122709716651985624, 1082323574100172800
Offset: 0
a(4)=3606 because 7^4+1 has divisors {1, 2, 1201, 2402}.
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a:=n->numtheory[sigma](7^n+1):
seq(a(n), n=0..100);
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DivisorSigma[1, 7^Range[0, 21] + 1] (* Paul F. Marrero Romero, Oct 16 2023 *)
A366617
Sum of the divisors of 5^n+1.
Original entry on oeis.org
3, 12, 42, 312, 942, 6264, 25284, 162000, 620460, 4961280, 16161768, 103442688, 367381884, 2441936064, 9859525284, 76963663296, 228970112844, 1526377433328, 6339280635408, 38199227335200, 144103649734968, 1285221510144000, 3894650946433800, 24349131482713344
Offset: 0
a(3)=312 because 5^3+1 has divisors {1, 2, 3, 6, 7, 9, 14, 18, 21, 42, 63, 126}.
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a:=n->numtheory[sigma](5^n+1):
seq(a(n), n=0..100);
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DivisorSigma[1, 5^Range[0, 30] + 1] (* Paolo Xausa, Jul 03 2024 *)
A366657
Sum of the divisors of 8^n+1.
Original entry on oeis.org
3, 13, 84, 800, 4356, 51792, 351120, 3100240, 17041416, 211053040, 1494039792, 12611914848, 73234343952, 794382536272, 5936210280000, 60037292774400, 282937726148616, 3264911394064320, 24128875076496960, 208532141890460960, 1225825603154905104
Offset: 0
a(4)=4356 because 8^4+1 has divisors {1, 17, 241, 4097}.
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a:=n->numtheory[sigma](8^n+1):
seq(a(n), n=0..100);
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DivisorSigma[1, 8^Range[0,20]+1] (* Paul F. Marrero Romero, Nov 19 2023 *)
A366669
a(n) = phi(10^n+1), where phi is Euler's totient function (A000010).
Original entry on oeis.org
1, 10, 100, 720, 9792, 90900, 990000, 9090900, 94117632, 681410880, 9897840000, 86925373920, 979102080000, 9080325951840, 95255567232000, 712493107200000, 9926748531589120, 90004044661864320, 989999010000000000, 9090909090909090900, 97910150554895155200
Offset: 0
Showing 1-7 of 7 results.