A318785 Numbers which are prime if each digit is replaced by its 9's complement.

2, 4, 6, 7, 10, 16, 20, 26, 28, 32, 38, 40, 46, 52, 56, 58, 62, 68, 70, 76, 80, 82, 86, 88, 92, 94, 96, 97, 112, 116, 118, 122, 136, 140, 142, 146, 160, 170, 172, 176, 178, 188, 190, 202, 212, 226, 230, 238, 242, 248, 256, 260, 266, 272, 280, 290, 298, 308, 316, 322, 326, 338, 340, 346, 352, 356, 358

Offset

1,1

Links

Table of n, a(n) for n=1..67.

Example

32 belongs to this sequence as its 9's complement is 67, which is prime.

Prog

(Python)
nmax=500
def is_prime(num):
    if num == 0 or num == 1: return(0)
    for k in range(2, num):
       if (num % k) == 0:
           return(0)
    return(1)
def c9(num):
    s=str(num)
    l=len(str(num))
    n=""
    for k in range(l):
        n = n+str(9-int(s[k]))
    return(int(n))
ris = ""
for i in range(2, nmax):
    if is_prime(c9(i)):
       ris = ris+str(i)+", "
print(ris)
(PARI) complement(n) = my(d=digits(n)); for(k=1, #d, d[k]=9-d[k]); subst(Pol(d), x, 10)
is(n) = ispseudoprime(complement(n)) \\ Felix Fröhlich, Sep 03 2018

Crossrefs

Cf. A061601 (9's complement of n).

Sequence in context: A026398 A374432 A179003 * A190206 A189287 A189128

Adjacent sequences: A318782 A318783 A318784 * A318786 A318787 A318788

Keyword

nonn,base

Author

Pierandrea Formusa, Sep 03 2018

Status

approved