A050505 -id:A050505 - cp's OEIS frontend

A265859 Unluckiness of n.

0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 3, 1, 0, 1, 2, 1, 0, 1, 4, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 3, 1, 2, 1, 0, 1, 5, 1, 2, 1, 0, 1, 0, 1, 2, 1, 6, 1, 4, 1, 2, 1, 3, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 3, 1, 2, 1, 7, 1, 0

Offset: 1

Max Barrentine, Dec 17 2015

nonn

If n is lucky, a(n)=0; if n is unlucky, a(n) is the step at which n is rejected from the lucky number sieve.

Max Barrentine, Table of n, a(n) for n = 1..10000

Cf. A000959, A050505, A145649, A260437, A260438.
Cf. also arrays A255543, A255545.
Cf. A271420 (analogous sequence).

(define (A265859 n) (* (- 1 (A145649 n)) (A260438 n))) ;; Antti Karttunen, Sep 11 2016

a(n) = (1-A145649(n)) * A260438(n). - Antti Karttunen, Sep 11 2016, corrected Nov 15 2019

A255544 Unlucky array, transposed.

Original entry on oeis.org

2, 5, 4, 19, 11, 6, 27, 39, 17, 8, 45, 57, 61, 23, 10, 55, 97, 91, 81, 29, 12, 85, 117, 147, 121, 103, 35, 14, 109, 177, 181, 199, 153, 123, 41, 16, 139, 225, 277, 243, 253, 183, 145, 47, 18, 157, 295, 345, 369, 315, 301, 217, 165, 53, 20, 175, 325, 447, 465, 471, 379, 351, 247, 187, 59, 22, 213, 381, 493, 603, 589, 567, 441, 403, 279, 207, 65, 24

Offset: 1

Antti Karttunen, Feb 25 2015

See comments at A255543.

Antti Karttunen, Table of n, a(n) for n = 1..5886; the first 108 antidiagonals of the array, flattened

Transpose: A255543.

Permutation of A050505.

rows = cols = 12; L = 2 Range[0, 2000] + 1; A = Join[{2 Range[cols]}, Reap[For[n = 2, n <= rows, r = L[[n++]]; L0 = L; L = ReplacePart[L, Table[r i -> Nothing, {i, 1, Length[L]/r}]]; Sow[Complement[L0, L][[1 ;; cols]]]]][[2, 1]]]; Table[A[[n - k + 1, k]], {n, 1, Min[rows, cols]}, {k, 1, n}] // Flatten (* Jean-François Alcover, Mar 15 2016 *)

(define (A255544 n) (A255543bi (A004736 n) (A002260 n))) ;; Other code as in A255543.

A266420 Odd unlucky numbers.

Original entry on oeis.org

5, 11, 17, 19, 23, 27, 29, 35, 39, 41, 45, 47, 53, 55, 57, 59, 61, 65, 71, 77, 81, 83, 85, 89, 91, 95, 97, 101, 103, 107, 109, 113, 117, 119, 121, 123, 125, 131, 137, 139, 143, 145, 147, 149, 153, 155, 157, 161, 165, 167, 173, 175, 177, 179, 181, 183, 185, 187, 191, 197, 199, 203, 207, 209, 213, 215, 217, 221, 225

Offset: 1

Antti Karttunen, Jan 28 2016

nonn

Antti Karttunen, Table of n, a(n) for n = 1..10000

Intersection of A005408 and A050505.
Cf. A145649, A257726.
Cf. also A071904, A266419

A309375 Unlucky palindromic primes.

Original entry on oeis.org

2, 5, 11, 101, 131, 181, 191, 313, 353, 373, 383, 757, 797, 919, 929, 10301, 10601, 11311, 11411, 12421, 12721, 12821, 13331, 13931, 14341, 14741, 15451, 15551, 16061, 16361, 16561, 16661, 17471, 17971, 18481, 19391, 19891, 19991, 30203, 30403, 30703, 30803

Offset: 1

Hauke Löffler, Jul 26 2019

			a(1) = 2 because 2 is both a palindromic prime (A002385) and an unlucky number (A050505).

Amiram Eldar, Table of n, a(n) for n = 1..5527 (terms below 10^9)

Intersection of A002385 and A050505.

Cf. A031881.

SageMath
```
[ p for p in A002385 if p in A050505 ]
```

4 wrong terms removed and more terms added by Amiram Eldar, May 14 2023

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A265859 Unluckiness of n.

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A255544 Unlucky array, transposed.

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A266420 Odd unlucky numbers.

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A309375 Unlucky palindromic primes.

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