A102141
Iccanobirt prime indices (11 of 15): Indices of prime numbers in A102121.
Original entry on oeis.org
4, 6, 7, 15, 25, 51, 126, 171, 311, 358, 865, 1850, 3311, 4686, 7893, 8249, 17795, 27176, 48728
Offset: 1
-
a[n_] := a[n] =
IntegerReverse[a[n - 1] + IntegerReverse[a[n - 2]] + IntegerReverse[a[n - 3]]];
a[0] = 0; a[1] = 0; a[2] = 1;
Select[Range[0, 5000], PrimeQ[a[#]] &] (* Robert Price, Apr 10 2020 *)
A102161
Iccanobirt primes (11 of 15): Prime numbers in A102121.
Original entry on oeis.org
2, 7, 31, 6367, 925189, 107197144969, 93402566446301441282188479643762853393, 3661745072013869917446592871282724637510478109647679973
Offset: 1
A102181
Iccanobirt semiprime indices (11 of 15): Indices of semiprime numbers in A102121.
Original entry on oeis.org
5, 11, 12, 17, 18, 37, 38, 43, 44, 45, 55, 61, 70, 93, 103, 110, 120, 129, 174, 198, 241, 245, 277, 303, 342, 381, 393, 552, 590, 657, 708
Offset: 1
-
nxt[{a_,b_,c_}]:={b,c,IntegerReverse[c+IntegerReverse[b]+IntegerReverse[a]]}; Flatten[ Position[NestList[nxt,{0,0,1},800][[;;,1]],?(PrimeOmega[#]==2&)]-1] (* _Harvey P. Dale, Mar 23 2023 *)
Offset changed to 1 and a(21)-a(31) from
Jinyuan Wang, Aug 14 2021
A102201
Iccanobirt semiprimes (11 of 15): Semiprime numbers in A102121.
Original entry on oeis.org
4, 581, 427, 8621, 16342, 253486367, 2219057821, 27297112754, 89359826467, 111725421271, 81491456587747, 65683774724947682, 3657883767310690921, 324958155565178050832783011, 7599185976546928443534740942821, 3638796960899657009455220564046301
Offset: 1
Offset changed to 1 and a(16) from
Jinyuan Wang, Aug 14 2021
A102113
Iccanobirt numbers (3 of 15): a(n) = a(n-1) + R(a(n-2)) + R(a(n-3)), where R is the digit reversal function A004086.
Original entry on oeis.org
0, 0, 1, 1, 2, 4, 7, 13, 24, 62, 135, 203, 760, 1593, 1962, 5980, 12622, 16208, 39724, 142606, 265660, 914694, 1587497, 2150478, 10594748, 27283111, 120773124, 216660897, 649176190, 1868619823, 2758358381, 6139199008, 11266906261
Offset: 0
-
R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
a:= proc(n) option remember; `if`(n<3, binomial(n, 2),
a(n-1) + R(a(n-2)) + R(a(n-3)) )
end:
seq(a(n), n=0..50); # Alois P. Heinz, Jun 18 2014
-
R[n_]:=FromDigits[Reverse[IntegerDigits[n]]];Clear[a];a[0]=0;a[1]=0;a[2]=1;a [n_]:=a[n]=a[n-1]+R[a[n-2]]+R[a[n-3]];Table[a[n], {n, 0, 40}]
nxt[{a1_,a2_,a3_}]:={a2,a3,a3+FromDigits[Reverse[IntegerDigits[ a1]]]+ FromDigits[ Reverse[ IntegerDigits[a2]]]}; Transpose[NestList[nxt,{0,0,1},40]][[1]] (* Harvey P. Dale, Oct 17 2012 *)
nxt[{a_,b_,c_}]:={b,c,c+IntegerReverse[b]+IntegerReverse[a]}; NestList[ nxt,{0,0,1},40][[All,1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 10 2016 *)
A102118
Iccanobirt numbers (8 of 15): a(n) = R(a(n-1) + a(n-2) + a(n-3)), where R is the digit reversal function A004086.
Original entry on oeis.org
0, 0, 1, 1, 2, 4, 7, 31, 24, 26, 18, 86, 31, 531, 846, 8041, 8149, 63071, 16297, 71578, 649051, 629637, 6620531, 9129987, 55108361, 97885807, 551421261, 924514407, 5741283751, 9149127127, 58252941851, 92725334137, 511304721061
Offset: 0
Cf.
A102111,
A102112,
A102113,
A102114,
A102115,
A102116,
A102117,
A102119,
A102120,
A102121,
A102122,
A102123,
A102124,
A102125.
-
R[n_]:=FromDigits[Reverse[IntegerDigits[n]]];Clear[a];a[0]=0;a[1]=0;a[2]=1;a [n_]:=a[n]=R[a[n-1]+a[n-2]+a[n-3]];Table[a[n], {n, 0, 40}]
Transpose[NestList[{#[[2]],#[[3]],FromDigits[Reverse[IntegerDigits[Total[ #]]]]}&,{0,0,1},40]][[1]] (* Harvey P. Dale, Dec 04 2012 *)
Showing 1-6 of 6 results.
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