A102276 -id:A102276 - cp's OEIS frontend

A018896 a(n) = ( a(n-1)*a(n-7) + a(n-4)^2 ) / a(n-8); a(0) = ... = a(7) = 1.

1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 9, 18, 34, 93, 180, 348, 724, 3033, 9666, 24986, 83761, 261033, 1023728, 3923791, 26128126, 105734485, 381740209, 1895904805, 14058722881, 97964968321, 517832518189, 4364261070929, 25225712161101, 181840424632390

Offset: 0

Michael Somos

From Vladimir Shevelev, Apr 04 2016: (Start)
For k >= 0, an infinite sequence {a(k,n)} of Somos's sequences (n>=0) is:
a(k,0) = a(k,1)= ... = a(k,2*k+1) = 1;
and then for n >= 2*k+2,
a(k,n) = (a(k,n-1)*a(k,n-2*k-1) + a(k,n-k-1)^2)/a(k,n-2*k-2).
In particular, {a(0,n)}=A006125, {a(1,n)}=A006720, {a(2,n)}=A102276, {a(3,n)}=A018896.
One can prove that the sequence {a(k,n)} has the first 4k+2 simple differences: 2k+1 zeros, after that k+1 1's and after that k consecutive squares, beginning with 2^2.
Further we have nontrivial differences. The first of them for k=0,1,2,... are 6, 16, 33, 59, 96, 146, 211, 293, 394, 516, ... that is, {k^3/3 + 5*k^2/2 + 43*k/6 + 6}.
(End)

T. D. Noe, Table of n, a(n) for n = 0..100
Mohamed Bensaid, Sato tau functions and construction of Somos sequence, arXiv:2409.05911 [math.NT], 2024. See p. 7.
David Gale, Mathematical Entertainments, Mathematical Intelligencer, volume 18, number 3, Summer 1996, page 25.
Eric Weisstein's World of Mathematics, Somos Sequence
Index entries for two-way infinite sequences

Cf. A006125, A006720, A102276.

a018896 n = a018896_list !! n
a018896_list = replicate 8 1 ++ f 8 where
   f x = ((a018896 (x - 1) * a018896 (x - 7) + a018896 (x - 4) ^ 2)
         `div` a018896 (x - 8)) : f (x + 1)
-- Reinhard Zumkeller, Oct 01 2012

[n le 8 select 1 else (Self(n-1)*Self(n-7)+Self(n-4)^2 ) / Self(n-8): n in [1..40]]; // Vincenzo Librandi, Dec 08 2016

f:= proc(n) option remember;
  if n <= 7 then 1 else
  (procname(n-1)*procname(n-7)+procname(n-4)^2)/procname(n-8)
  fi
end proc:
seq(f(n),n=0..50); # Robert Israel, Apr 04 2016

RecurrenceTable[{a[1]==a[2]==a[3]==a[4]==a[5]==a[6]==a[7]==a[8]==1, a[n]==(a[n-1]a[n-7]+ a[n-4]^2)/a[n-8]},a[n],{n,50}] (* Harvey P. Dale, May 02 2011 *)
k = 3; Set[#, 1] & /@ Map[a[k, #] &, Range[0, 2 k + 1]]; a[k_, n_] /; n >= 2 k + 2 := (a[k, n - 1] a[k, n - 2 k - 1] + a[k, n - k - 1]^2)/ a[k, n - 2 k - 2]; Table[a[k, n], {n, 0, 35}] (* Michael De Vlieger, Apr 04 2016 *)

More terms from Harvey P. Dale, May 02 2011

A271831 Somos's sequence {a(6,n)} defined in comment in A018896: a(0)=a(1)= ... = a(13) = 1; for n>=14, a(n) = (a(n-1)*a(n-13) + a(n-7)^2)/a(n-14).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 12, 21, 37, 62, 98, 147, 358, 609, 959, 1541, 2618, 4655, 8407, 28631, 81011, 186528, 376741, 706041, 1280174, 3598503, 8411236, 24021605, 74880071, 219318499, 580374907, 1400227135, 6308924342

Offset: 0

Vladimir Shevelev and Peter J. C. Moses, Apr 15 2016

nonn

Seiichi Manyama, Table of n, a(n) for n = 0..416
Eric Weisstein's World of Mathematics, Somos Sequence

Cf. A018896, A006125, A006720, A102276, A271341, A271835, A271837, A271838, A271839.

[n le 14 select 1 else (Self(n-1)*Self(n-13) + Self(n-7)^2)/Self(n-14): n in [1..50]]; // G. C. Greubel, Feb 21 2018

a[n_ /; 0 <= n <= 14] = 1; a[n_]:= a[n] = (a[n-1]*a[n-13] + a[n-7]^2)/a[n -14]; Table[a[n], {n,0,50}] (* G. C. Greubel, Feb 21 2018 *)

{a(n) = if(n<= 14, 1, (a(n-1)*a(n-13) + a(n-7)^2)/a(n-14))};
for(n=1,50, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018

A271341 Somos's sequence {a(4,n)} defined in comment in A018896.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 10, 19, 35, 60, 156, 284, 499, 930, 1836, 7116, 21586, 52869, 115344, 356076, 972840, 3350009, 11844969, 37689894, 215136930, 785604755, 2444023816, 7985904285, 36968693334, 230985863335, 1429813280831, 6838592493455, 27144055289355, 191201731942399

Offset: 0

Vladimir Shevelev and Peter J. C. Moses, Apr 04 2016

nonn

The sequence of the first differences begins from 9 zeros, 5 1's and 4 consecutive squares, beginning with 2^2.

A generalization see in the comment in A018896.

Seiichi Manyama, Table of n, a(n) for n = 0..318

Cf. A018896, A006720, A102276, A271835, A271831, A271837, A271838, A271839.

[n le 10 select 1 else (Self(n-1)*Self(n-9) + Self(n-5)^2 )/Self(n-10): n in [1..40]]; // G. C. Greubel, Feb 21 2018

k = 4; Set[#, 1] & /@ Map[a[k, #] &, Range[0, 2 k + 1]]; a[k_, n_] /;
n >= 2 k + 2 := (a[k, n - 1] a[k, n - 2 k - 1] + a[k, n - k - 1]^2) / a[k, n - 2 k - 2]; Table[a[k, n], {n, 0, 42}] (* Michael De Vlieger, Apr 04 2016 *)
a[n_ /; 0 <= n <= 10] = 1; a[n_]:= a[n] = (a[n-1]*a[n-9] + a[n-5]^2)/a[n -10]; Table[a[n], {n,0,40}] (* G. C. Greubel, Feb 21 2018 *)

{a(n) = if(n< 10, 1, (a(n-1)*a(n-9) + a(n-5)^2)/a(n-10))};
for(n=0,40, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018

More terms from Michael De Vlieger, Apr 04 2016

A271835 Somos's sequence {a(5,n)} defined in comment in A018896: a(0)=a(1)= ... = a(11) = 1; for n>=12, a(n) = (a(n-1)*a(n-11) + a(n-6)^2)/a(n-12).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 11, 20, 36, 61, 97, 243, 425, 700, 1199, 2183, 4115, 14902, 43515, 102827, 214168, 418685, 1223440, 3053628, 9484929, 31351174, 95335734, 260010845, 1305343146, 4437434637, 12553187856, 35704506092

Offset: 0

Vladimir Shevelev and Peter J. C. Moses, Apr 15 2016

nonn

Seiichi Manyama, Table of n, a(n) for n = 0..368
Eric Weisstein's World of Mathematics, Somos Sequence

Cf. A018896, A006125, A006720, A102276, A271341, A271831, A271837, A271838, A271839.

[n le 12 select 1 else (Self(n-1)*Self(n-11) + Self(n-6)^2 )/Self(n-12): n in [1..50]]; // G. C. Greubel, Feb 21 2018

a[k_,n_]:=a[k,n]= If[n>2k+1,(a[k,(n-1)]*a[k,(n-2k-1)]+(a[k,(n-k-1)])^2 )/a[k,(n-2k-2)],1]; Map[a[5,#]&,Range[0,43]] (* Peter J. C. Moses, Apr 15 2016 *)
RecurrenceTable[{Table[a[i]==1,{i,0,11}],a[n]==(a[n-1]a[n-11]+a[n-6]^2)/ a[n-12]},a,{n,50}](* Harvey P. Dale, Sep 24 2021 *)

{a(n) = if(n< 12, 1, (a(n-1)*a(n-11) + a(n-6)^2)/a(n-12))};
for(n=0,50, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018

More terms from Alois P. Heinz, Apr 15 2016

A271837 Somos's sequence {a(7,n)} defined in comment in A018896: a(0)=a(1)= ... = a(15) = 1; for n>=16, a(n) = (a(n-1)*a(n-15)+ a(n-8)^2)/a(n-16).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 13, 22, 38, 63, 99, 148, 212, 505, 842, 1284, 1966, 3153, 5312, 9200, 15968, 51401, 141522, 319386, 631223, 1149722, 2003800, 3442200, 9402302, 20908517, 55671036, 164685883, 466783858

Offset: 0

Vladimir Shevelev and Peter J. C. Moses, Apr 15 2016

nonn

Seiichi Manyama, Table of n, a(n) for n = 0..463
Eric Weisstein's World of Mathematics, Somos Sequence

Cf. A018896, A006125, A006720, A102276, A271341, A271831, A271835, A271838, A271839.

[n le 16 select 1 else (Self(n-1)*Self(n-15) + Self(n-8)^2 )/Self(n-16): n in [1..50]]; // G. C. Greubel, Feb 21 2018

a[k_,n_]:=a[k,n] = If[n>2*k+1,(a[k,(n-1)]*a[k,(n-2*k-1)]+(a[k,(n-k-1)])^2 )/a[k,(n-2*k-2)],1]; Map[a[7,#]&,Range[0,50]] (* Peter J. C. Moses, Apr 15 2016 *)

{a(n) = if(n< 16, 1, (a(n-1)*a(n-15) + a(n-8)^2)/a(n-16))};
for(n=0,50, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018

A271838 Somos's sequence {a(8,n)} defined in comment in A018896: a(0)=a(1)= ... = a(17) = 1; for n>=18, a(n) = (a(n-1)*a(n-17)+ a(n-9)^2)/a(n-18).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, 23, 39, 64, 100, 149, 213, 294, 688, 1130, 1683, 2484, 3800, 6100, 10143, 17082, 28584, 87352, 234714, 521145, 1013424, 1809100, 3067659, 5075784, 8375940, 22379904, 47848348

Offset: 0

Vladimir Shevelev and Peter J. C. Moses, Apr 15 2016

nonn

Seiichi Manyama, Table of n, a(n) for n = 0..510
Eric Weisstein's World of Mathematics, Somos Sequence

Cf. A018896, A006125, A006720, A102276, A271341, A271835, A271831, A271837, A271839.

[n le 18 select 1 else (Self(n-1)*Self(n-17) + Self(n-9)^2 )/Self(n-18): n in [1..40]]; // G. C. Greubel, Feb 21 2018

a[k_,n_]:=a[k,n] = If[n>2*k+1,(a[k,(n-1)]*a[k,(n-2*k-1)]+(a[k,(n-k-1)])^2 )/a[k,(n-2*k-2)],1]; Map[a[8,#]&,Range[0,50]] (* Peter J. C. Moses, Apr 15 2016 *)
RecurrenceTable[{a[0]==a[1]==a[2]==a[3]==a[4]==a[5]==a[6]==a[7]==a[8]==a[9]== a[10]==a[11]==a[12]==a[13]==a[14]==a[15]==a[16]==a[17]==1,a[n]==(a[n-1]a[n-17]+ a[n-9]^2)/a[n-18]},a,{n,60}] (* Harvey P. Dale, Jun 30 2023 *)

{a(n) = if(n< 18, 1, (a(n-1)*a(n-17) + a(n-9)^2)/a(n-18))};
for(n=0,40, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018

A271839 Somos's sequence {a(9,n)} defined in comment in A018896: a(0)= a(1) = ... = a(19) = 1; for n >= 20, a(n) = (a(n-1)*a(n-19) + a(n-10)^2)/a(n-20).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 15, 24, 40, 65, 101, 150, 214, 295, 395, 911, 1479, 2164, 3105, 4571, 7033, 11252, 18383, 30095, 48707, 141866, 372815, 816479, 1567804, 2757573, 4585139, 7385515

Offset: 0

Vladimir Shevelev and Peter J. C. Moses, Apr 15 2016

nonn

Seiichi Manyama, Table of n, a(n) for n = 0..555
Eric Weisstein's World of Mathematics, Somos Sequence

Cf. A018896, A006125, A006720, A102276, A271341, A271835, A271831, A271837, A271838.

[n le 20 select 1 else (Self(n-1)*Self(n-19) + Self(n-10)^2 )/Self(n-20): n in [1..50]]; // G. C. Greubel, Feb 21 2018

a[k_,n_]:=a[k,n]=If[n>2k+1,(a[k,(n-1)]*a[k,(n-2k-1)]+(a[k,(n-k-1)])^2)/a[k,(n-2k-2)],1];
Map[a[9,#]&,Range[0,70]] (* Peter J. C. Moses, Apr 15 2016 *)

{a(n) = if(n< 20, 1, (a(n-1)*a(n-19) + a(n-10)^2)/a(n-20))};
for(n=0,50, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018

A256858 a(n) = (-a(n-1) * a(n-6) + a(n-2) * a(n-5)) / a(n-7) with a(n) = 1 if abs(n) < 4, a(11) = 4.

Original entry on oeis.org

1, 1, 1, 1, 0, 1, -1, 2, -3, 3, -3, 4, -2, 8, 9, 17, 29, 50, 83, 107, 56, 239, -243, 1103, -2351, 3775, -7227, 14463, -18648, 55283, 54011, 256666, 698301, 2059753, 5324929, 9820288, 15128062, 55075036, -28437275, 503857819, -1438167267, 4083736906

Offset: 0

Michael Somos, Apr 12 2015

sign

Similar to the Somos-6 and Somos-7 sequences with many bilinear identities.

G. C. Greubel, Table of n, a(n) for n = 0..416

Cf. A102276, A256916.

I:=[-2,8,9,17,29,50,83]; [1, 1, 1, 1, 0, 1, -1, 2, -3, 3, -3, 4] cat [n le 7 select I[n] else (-Self(n-1)*Self(n-6) + Self(n-2)*Self(n-5))/Self(n-7): n in [1..30]]; // G. C. Greubel, Aug 03 2018

Join[{1, 1, 1, 1, 0, 1, -1, 2, -3, 3, -3, 4}, RecurrenceTable[{a[n] == (-a[n - 1]*a[n - 6] + a[n - 2]*a[n - 5])/a[n - 7], a[12] == -2, a[13] == 8, a[14] == 9, a[15] == 17, a[16] == 29, a[17] == 50, a[18] == 83}, a, {n, 12, 60}]] (* G. C. Greubel, Aug 03 2018 *)
a[n_] := Which[n<0, a[-n], n<12, {1, 1, 1, 1, 0, 1, -1, 2, -3, 3, -3, 4}[[1+n]], True, a[n] = (-a[n-1]*a[n-6] + a[n-2]*a[n-5])/a[n-7]]; (* Michael Somos, Dec 16 2023 *)

{a(n) = my(an); n = abs(n)+1; an = concat([ 1, 1, 1, 1, 0, 1, -1, 2, -3, 3, -3, 4], vector(max(0, n-12), k)); for(k=13, n, an[k] = (-an[k-1] * an[k-6] + an[k-2] * an[k-5]) / an[k-7]); an[n]};

{a(n) = my(an); n = abs(n)+1; an = vector(n, k, 1); if( n>=5, an[5] = 0); if( n>=7, an[7] = -1); if( n>=8, an[8] = 2); for(k=9, n, an[k] = if( k==12, 4, (-an[k-1] * an[k-6] + an[k-2] * an[k-5]) / an[k-7])); an[n]};

a(2*n - 5) = A102276(n) for all n in Z.
a(2*n) = A256916(n) for all n in Z.
a(n) = a(-n) for all n in Z.
0 = a(n) * a(n+7) + a(n+1) * a(n+6) - a(n+2) * a(n+5) for all n in Z.
0 = a(n) * a(n+8) - a(n+2) * a(n+6) - a(n+4)^2 + (2 - mod(n,2)) * a(n+3) * a(n+5) for all n in Z.
0 = a(n) * a(n+11) + a(n+1) * a(n+10) + a(n+5) * a(n+6) for all n in Z. - Michael Somos, Apr 14 2015

A256916 a(n) = (a(n-1) * a(n-5) + a(n-3)^2) / a(n-6) with a(0) = a(1) = 1, a(2) = 0, a(3) = -1, a(4) = -3, a(8) = 29.

Original entry on oeis.org

1, 1, 0, -1, -3, -3, -2, 9, 29, 83, 56, -243, -2351, -7227, -18648, 54011, 698301, 5324929, 15128062, -28437275, -1438167267, -14356619593, -108319050672, 80689859625, 13472837856577, 268773209122329, 2678522836045616, 7565687047045511, -672545703786704803

Offset: 0

Michael Somos, Apr 13 2015

sign

Similar to the Somos-6 and Somos-7 sequences with many bilinear identities.

G. C. Greubel, Table of n, a(n) for n = 0..208

Cf. A102276, A256858.

I:=[83, 56, -243, -2351, -7227, -18648]; [1,1,0,-1,-3,-3,-2,9,29] cat [n le 6 select I[n] else (Self(n-1)*Self(n-5) + Self(n-3)^2)/ Self(n-6): n in [1..30]]; // G. C. Greubel, Aug 03 2018

Join[{1,1,0,-1,-3,-3,-2,9,29}, RecurrenceTable[{a[n] == (a[n-1]*a[n-5] + a[n-3]^2)/a[n-6], a[9] == 83, a[10] == 56, a[11] == -243, a[12] == -2351, a[13] == -7227, a[14] == -18648}, a, {n, 9, 60}]] (* G. C. Greubel, Aug 03 2018 *)

{a(n) = my(an); n = abs(n)+1; an = concat([ 1, 1, 0, -1, -3, -3, -2, 9, 29], vector(max(0, n-9), k)); for(k=10, n, an[k] = (an[k-1] * an[k-5] + an[k-3]^2) / an[k-6]); an[n]};

a(n) = a(-n) for all n in Z.
a(n) = A256858(2*n) for all n in Z.
Let b(n) = A102276(n). Then 0 = a(n) * b(n) - a(n+2) * b(n-2) + a(n+3) * b(n-3) for all n in Z.
0 = a(n) * a(n+6) - a(n+1) * a(n+5) - a(n+3) * a(n+3) for all n in Z.
0 = a(n) * a(n+9) + a(n+2) * a(n+7) - a(n+3) * a(n+6) - 9 * a(n+4) * a(n+5) for all n in Z.

A276529 a(n) = (a(n-1) * a(n-5) + 1) / a(n-6), a(0) = a(1) = ... = a(5) = 1.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 13, 20, 27, 34, 41, 89, 137, 185, 233, 281, 610, 939, 1268, 1597, 1926, 4181, 6436, 8691, 10946, 13201, 28657, 44113, 59569, 75025, 90481, 196418, 302355, 408292, 514229, 620166, 1346269, 2072372, 2798475, 3524578, 4250681, 9227465

Offset: 0

Seiichi Manyama, Nov 16 2016

Thanks to the linear recurrence signature, we see that this is actually five separate linear recurrence sequences, each with signature (7,-1), interwoven together. - Greg Dresden, Oct 16 2021

Seiichi Manyama, Table of n, a(n) for n = 0..5985
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,7,0,0,0,0,-1).

Cf. A275173, A102276, A276530.

5th-sections: A049685, A033891, A033889.

LinearRecurrence[{0,0,0,0,7,0,0,0,0,-1}, {1,1,1,1,1,1,2,3,4,5}, 50] (* G. C. Greubel, Nov 18 2016 *)
RecurrenceTable[{a[0]==a[1]==a[2]==a[3]==a[4]==a[5]==1,a[n]==(a[n-1]a[n-5]+ 1)/a[n-6]},a,{n,50}] (* Harvey P. Dale, Oct 08 2020 *)
Flatten[Table[{LucasL[4 n - 2]/3, Fibonacci[4 n - 1], LucasL[4 n + 2]/3 - Fibonacci[4 n], LucasL[4 n - 2]/3 + Fibonacci[4 n], Fibonacci[4 n + 1]}, {n, 0, 10}]] (* Greg Dresden, Oct 16 2021 *)

Vec((1 +x +x^2 +x^3 +x^4 -6*x^5 -5*x^6 -4*x^7 -3*x^8 -2*x^9)/(1 -7*x^5 +x^10) + O(x^50)) \\ Colin Barker, Nov 16 2016

def A(k, m, n)
  a = Array.new(2 * k, 1)
  ary = [1]
  while ary.size < n + 1
    i = a[-1] * a[1] + a[k] ** m
    break if i % a[0] > 0
    a = *a[1..-1], i / a[0]
    ary << a[0]
  end
  ary
end
def A276529(n)
  A(3, 0, n)
end

a(n) + a(n+10) = 7*a(n+5).
a(5-n) = a(n).
G.f.: (1 +x +x^2 +x^3 +x^4 -6*x^5 -5*x^6 -4*x^7 -3*x^8 -2*x^9) / (1 -7*x^5 +x^10). - Colin Barker, Nov 16 2016
From Greg Dresden, Oct 16 2021: (Start)
a(5*n) = L(4*n-2)/3 = A049685(n-1),
a(5*n+1) = F(4*n-1) = A033891(n-1),
a(5*n+2) = L(4*n+2)/3 - F(4*n),
a(5*n+3) = L(4*n-2)/3 + F(4*n),
a(5*n+4) = F(4*n+1) = A033889(n). (End)

cp's OEIS Frontend

A018896 a(n) = ( a(n-1)*a(n-7) + a(n-4)^2 ) / a(n-8); a(0) = ... = a(7) = 1.

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A271831 Somos's sequence {a(6,n)} defined in comment in A018896: a(0)=a(1)= ... = a(13) = 1; for n>=14, a(n) = (a(n-1)*a(n-13) + a(n-7)^2)/a(n-14).

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A271341 Somos's sequence {a(4,n)} defined in comment in A018896.

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A271835 Somos's sequence {a(5,n)} defined in comment in A018896: a(0)=a(1)= ... = a(11) = 1; for n>=12, a(n) = (a(n-1)*a(n-11) + a(n-6)^2)/a(n-12).

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A271837 Somos's sequence {a(7,n)} defined in comment in A018896: a(0)=a(1)= ... = a(15) = 1; for n>=16, a(n) = (a(n-1)*a(n-15)+ a(n-8)^2)/a(n-16).

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A271838 Somos's sequence {a(8,n)} defined in comment in A018896: a(0)=a(1)= ... = a(17) = 1; for n>=18, a(n) = (a(n-1)*a(n-17)+ a(n-9)^2)/a(n-18).

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A271839 Somos's sequence {a(9,n)} defined in comment in A018896: a(0)= a(1) = ... = a(19) = 1; for n >= 20, a(n) = (a(n-1)*a(n-19) + a(n-10)^2)/a(n-20).

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A256858 a(n) = (-a(n-1) * a(n-6) + a(n-2) * a(n-5)) / a(n-7) with a(n) = 1 if abs(n) < 4, a(11) = 4.

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