

A005145


n copies of nth prime.


8



2, 3, 3, 5, 5, 5, 7, 7, 7, 7, 11, 11, 11, 11, 11, 13, 13, 13, 13, 13, 13, 17, 17, 17, 17, 17, 17, 17, 19, 19, 19, 19, 19, 19, 19, 19, 23, 23, 23, 23, 23, 23, 23, 23, 23, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31
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OFFSET

1,1


COMMENTS

Seen as a triangle read by rows: T(n,k) = A000040(n), 1 <= k <= n; row sums = A033286; central terms = A031368.  Reinhard Zumkeller, Aug 05 2009
Seen as a square array read by antidiagonals, a subtable of the binary operation multiplication tables A297845, A306697 and A329329.  Peter Munn, Jan 15 2020


REFERENCES

Douglas Hofstadter, "Fluid Concepts and Creative Analogies: Computer Models of the Fundamental Mechanisms of Thought", Basic Books, 1995.


LINKS

Reinhard Zumkeller, Rows n = 1..125 of triangle, flattened


FORMULA

From Joseph Biberstine (jrbibers(AT)indiana.edu), Aug 14 2006: (Start)
a(n) = prime(floor(1/2 + sqrt(2*n))).
a(n) = A000040(A002024(n)). (End)
From Peter Munn, Jan 15 2020: (Start)
When viewed as a square array A(n,k), the following hold for n >= 1, k >= 1:
A(n,k) = prime(n+k1).
A(n,1) = A(1,n) = prime(n), where prime(n) = A000040(n).
A(n+1,k) = A(n,k+1) = A003961(A(n,k)).
A(n,k) = A297845(A(n,1), A(1,k)) = A306697(A(n,1), A(1,k)) = A329329(A(n,1), A(1,k)).
(End)
Sum_{n>=1} 1/a(n)^2 = A097906.  Amiram Eldar, Aug 16 2022


EXAMPLE

Triangle begins:
2;
3, 3;
5, 5, 5;
7, 7, 7, 7;
...


MATHEMATICA

Table[Prime[Floor[1/2 + Sqrt[2*n]]], {n, 1, 80}] (* Joseph Biberstine (jrbibers(AT)indiana.edu), Aug 14 2006 *)
Flatten[Table[Table[Prime[n], {n}], {n, 12}]] (* Alonso del Arte, Jan 18 2012 *)


PROG

(Haskell)
a005145 n k = a005145_tabl !! (n1) !! (k1)
a005145_row n = a005145_tabl !! (n1)
a005145_tabl = zipWith ($) (map replicate [1..]) a000040_list
a005145_list = concat a005145_tabl
 Reinhard Zumkeller, Jul 12 2014, Mar 18 2011, Oct 17 2010
(PARI) a(n) = prime(round(sqrt(2*n))) \\ Charles R Greathouse IV, Oct 23 2015
(Magma) [NthPrime(Round(Sqrt(2*n))): n in [1..60]]; // Vincenzo Librandi, Jan 18 2020
(Python)
from sympy import primerange
a = []; [a.extend([pn]*n) for n, pn in enumerate(primerange(1, 32), 1)]
print(a) # Michael S. Branicky, Jul 13 2022


CROSSREFS

Sequences with similar definitions: A002024, A175944.
Cf. A000040 (range of values), A003961, A031368 (main diagonal), A033286 (row sums), A097906.
Subtable of A297845, A306697, A329329.
Sequence in context: A053046 A261179 A066658 * A280740 A156350 A076367
Adjacent sequences: A005142 A005143 A005144 * A005146 A005147 A005148


KEYWORD

nonn,nice,tabl


AUTHOR

Russ Cox


STATUS

approved



