A090537 -id:A090537 - cp's OEIS frontend

A090538 Location of 3 in A090537, or 0 if A090537 is 0.

1, 1, 1, 0, 1, 4, 0, 2, 1, 0, 1, 7, 0, 14, 0, 0, 7, 2, 0, 2, 20, 0, 6, 1, 0, 0, 25, 0, 2, 3, 0, 0, 12, 0, 3, 24, 0, 22, 2, 0, 0, 14, 0, 17, 32, 0, 29, 6, 0, 16, 19, 0, 7, 9, 0, 33, 19, 0, 31, 3, 0, 26, 4, 0, 61, 31, 0, 0, 45, 0, 5, 29, 0, 5, 63, 0, 20, 39, 0, 9, 40, 0, 71, 1, 0, 4, 25, 0, 6, 4, 0, 41

Offset: 1

Amarnath Murthy, Dec 08 2003

a(3n+1) = 0.

Cf. A090535, A090536, A090537.

More terms from David Wasserman, Jan 03 2006

A090535 Least n-digit prime using digit 7 once and rest all 1, or 0 if no such prime exists.

Original entry on oeis.org

7, 17, 0, 1117, 11117, 0, 1111711, 11111117, 0, 1117111111, 17111111111, 0, 1111171111111, 0, 0, 0, 11111111111111171, 0, 1111111111111111171, 11111111111111117111, 0, 1111111111111111111711, 11111111111111111111117

Offset: 1

Amarnath Murthy, Dec 08 2003

a(3n) = 0.

			a(5) = 11117.

Cf. A090536, A090537, A090538.

More terms from David Wasserman, Jan 03 2006

A090536 Location of 7 in A090535, or 0 if A090535 is 0.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 3, 1, 0, 7, 10, 0, 8, 0, 0, 0, 2, 0, 2, 4, 0, 3, 1, 0, 6, 7, 0, 8, 1, 0, 8, 4, 0, 3, 5, 0, 8, 0, 0, 1, 0, 0, 20, 30, 0, 15, 16, 0, 6, 13, 0, 43, 10, 0, 15, 55, 0, 11, 7, 0, 22, 6, 0, 2, 10, 0, 34, 43, 0, 7, 11, 0, 63, 56, 0, 0, 14, 0, 58, 19, 0, 56, 29, 0, 29, 42, 0, 51, 4, 0, 30

Offset: 1

Amarnath Murthy, Dec 08 2003

a(3n) = 0.

			a(10) = 7 as A090535(10) = 1117111111.

Cf. A090535, A090537, A090538.

More terms from David Wasserman, Jan 03 2006

A342221 Integers k, not congruent to 1 mod 3, such that there is no prime of length k using digit 3 once and rest all 1.

Original entry on oeis.org

15, 26, 32, 41, 68, 93, 99, 113, 116, 119, 134, 150, 158, 161, 170, 173, 176, 177, 179, 204, 213, 252, 257, 266, 284, 299, 305, 312, 320, 333, 353, 357, 374, 392, 402, 404, 419, 434, 443, 450, 491, 495, 506, 509, 513, 518, 527, 548, 551, 554, 570, 582, 584, 593

Offset: 1

Michel Marcus, Mar 14 2021

The "not congruent to 1 mod 3" condition is due to the fact that A090537(3*k+1) = 0.

Cf. A090537, A107689.

Subsequence of A007494.

from sympy import isprime
A342221_list = []
for k in range(1,10**3):
    if k % 3 != 1:
        m, l = (10**k-1)//9, 2
        for i in range(k):
            if isprime(m+l):
                break
            l *= 10
        else:
            A342221_list.append(k) # Chai Wah Wu, Mar 15 2021

More terms from Chai Wah Wu, Mar 15 2021

cp's OEIS Frontend

A090538 Location of 3 in A090537, or 0 if A090537 is 0.

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A090535 Least n-digit prime using digit 7 once and rest all 1, or 0 if no such prime exists.

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A090536 Location of 7 in A090535, or 0 if A090535 is 0.

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A342221 Integers k, not congruent to 1 mod 3, such that there is no prime of length k using digit 3 once and rest all 1.

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