A156127 -id:A156127 - cp's OEIS frontend

A250656 T(n,k)=Number of (n+1)X(k+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.

9, 16, 19, 25, 34, 39, 36, 53, 70, 79, 49, 76, 109, 142, 159, 64, 103, 156, 221, 286, 319, 81, 134, 211, 316, 445, 574, 639, 100, 169, 274, 427, 636, 893, 1150, 1279, 121, 208, 345, 554, 859, 1276, 1789, 2302, 2559, 144, 251, 424, 697, 1114, 1723, 2556, 3581

Offset: 1

R. H. Hardin, Nov 26 2014

Table starts
....9...16....25....36....49....64....81...100...121...144...169....196....225
...19...34....53....76...103...134...169...208...251...298...349....404....463
...39...70...109...156...211...274...345...424...511...606...709....820....939
...79..142...221...316...427...554...697...856..1031..1222..1429...1652...1891
..159..286...445...636...859..1114..1401..1720..2071..2454..2869...3316...3795
..319..574...893..1276..1723..2234..2809..3448..4151..4918..5749...6644...7603
..639.1150..1789..2556..3451..4474..5625..6904..8311..9846.11509..13300..15219
.1279.2302..3581..5116..6907..8954.11257.13816.16631.19702.23029..26612..30451
.2559.4606..7165.10236.13819.17914.22521.27640.33271.39414.46069..53236..60915
.5119.9214.14333.20476.27643.35834.45049.55288.66551.78838.92149.106484.121843

			Some solutions for n=4 k=4
..1..1..0..1..1....0..0..0..0..0....0..0..0..0..0....1..1..1..0..0
..0..0..0..1..1....1..1..1..1..1....1..1..1..1..1....0..0..0..0..0
..0..0..0..1..1....1..1..1..1..1....0..0..0..0..0....0..0..0..0..0
..0..0..0..1..1....0..0..0..0..0....1..1..1..1..1....1..1..1..1..1
..0..0..0..1..1....0..1..1..1..1....1..1..1..1..1....0..0..0..1..1

R. H. Hardin, Table of n, a(n) for n = 1..880

Column 1 is A052549(n+1)
Column 2 is A176449
Column 3 is A156127(n+1)
Column 4 is A048487(n+2)
Row 1 is A000290(n+2)
Row 2 is A168244(n+3)

Empirical: T(n,k) = 2^(n-1)*k^2 + (5*2^(n-1)-1)*k + 2^(n+1)
Empirical for column k:
k=1: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1) +(5*2^(n-1) -1) +2^(n+1)
k=2: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1)*4 +(5*2^(n-1) -1)*2 +2^(n+1)
k=3: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1)*9 +(5*2^(n-1) -1)*3 +2^(n+1)
k=4: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1)*16 +(5*2^(n-1) -1)*4 +2^(n+1)
k=5: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1)*25 +(5*2^(n-1) -1)*5 +2^(n+1)
k=6: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1)*36 +(5*2^(n-1) -1)*6 +2^(n+1)
k=7: a(n) = 3*a(n-1) -2*a(n-2); also a(n) = 2^(n-1)*49 +(5*2^(n-1) -1)*7 +2^(n+1)
Empirical for row n:
n=1: a(n) = 1*n^2 + 4*n + 4
n=2: a(n) = 2*n^2 + 9*n + 8
n=3: a(n) = 4*n^2 + 19*n + 16
n=4: a(n) = 8*n^2 + 39*n + 32
n=5: a(n) = 16*n^2 + 79*n + 64
n=6: a(n) = 32*n^2 + 159*n + 128
n=7: a(n) = 64*n^2 + 319*n + 256

A225582 Primes in the chain of repeated application of x->2*x+3, starting at x=11.

Original entry on oeis.org

11, 53, 109, 1789, 3581, 28669, 229373, 3670013, 58720253, 117440509, 60129542141, 264452523040700131966973, 34662321099990647697175478269, 2381976568446569244243622252022377480189, 4878288012178573812210938372141829079433213

Offset: 1

Vincenzo Librandi, May 14 2013

Primes in A156127.

Vincenzo Librandi, Table of n, a(n) for n = 1..26

Primes of the form k*2^m-3: A050415 (k=1), A173769 (k=5), this sequence (k=7), A225583 (k=11), A225584 (k=13); A172156 (k=100), A163589 (k=715).

Numbers of the form 7*2^m-3: A156127.

x:=11; a:=[n eq 1 select x else 2*Self(n-1)+3: n in [1..200]]; [a[i]: i in [1..#a] | IsPrime(a[i])];

[a: n in [0..150] | IsPrime(a) where a is 7*2^n-3];

Select[NestList[2 # + 3 &, 11, 30], PrimeQ] (* or *) Select[Table[7 2^n - 3, {n, 0, 150}], PrimeQ]

A127703 Primes of the form 72^k-3 or 72^k+3.

Original entry on oeis.org

11, 17, 31, 53, 59, 109, 227, 1789, 3581, 28669, 57347, 114691, 229373, 3670013, 14680067, 58720253, 117440509, 7516192771, 60129542141, 7881299347898371, 264452523040700131966973, 34662321099990647697175478269

Offset: 1

J. M. Bergot, Sep 27 2011

nonn

This sequence lists the primes produced by the sum of three consecutive powers of 2 minus 3 or plus 3, 2^k+2^(k+1)+2^(k+2)+-3, generated by k = 1, 1, 2, 3, 3, 4, 5, 8, 9, 12, 13, 14, 15, 19, 21, 23, 24, 30, 33...

In 76 trials from k=0 to 37, 19 primes, 34 semiprimes, and 23 numbers requiring more than two different prime factors were produced. This differs from the distribution of such numbers. Starting at k=16 the final digits of the sum are the powers of 2 from 1 to 13.

			2^5 + 2^6 + 2^7=224, then 224-3=221=semiprime 13*17 (not contributing to the sequence) or 224+3=prime 227, an entry in the sequence.

Cf. A156127, A164285.

lim = 100; Union[Select[7*2^Range[lim] - 3, PrimeQ], Select[7*2^Range[lim] + 3, PrimeQ]] (* T. D. Noe, Sep 27 2011 *)

Entries corrected by R. J. Mathar, Sep 27 2011

cp's OEIS Frontend

A250656 T(n,k)=Number of (n+1)X(k+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.

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A225582 Primes in the chain of repeated application of x->2*x+3, starting at x=11.

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A127703 Primes of the form 72^k-3 or 72^k+3.

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cp's OEIS Frontend

A250656 T(n,k)=Number of (n+1)X(k+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.

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Author

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Comments

Examples

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Crossrefs

Formula

A225582 Primes in the chain of repeated application of x->2*x+3, starting at x=11.

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Magma

Magma

Mathematica

A127703 Primes of the form 7*2^k-3 or 7*2^k+3.

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Mathematica

Extensions

A127703 Primes of the form 72^k-3 or 72^k+3.