A088999 Flip 6,9 numbers: if number k contains decimal digit '6' or '9', then flip all occurrences of '6' to '9' and vice versa.

9, 6, 19, 16, 29, 26, 39, 36, 49, 46, 59, 56, 90, 91, 92, 93, 94, 95, 99, 97, 98, 96, 79, 76, 89, 86, 60, 61, 62, 63, 64, 65, 69, 67, 68, 66, 109, 106, 119, 116, 129, 126, 139, 136, 149, 146, 159, 156, 190, 191, 192, 193, 194, 195, 199, 197, 198, 196, 179, 176, 189

Offset: 1

Author

Cino Hilliard, Nov 02 2003

Keywords

• nonn
• base

Comments

For digits d of n if d = 6 make it 9 else if d = 9 make it 6.

However, numbers containing neither digit 6 nor 9 are not terms (cf. A222251).

Crossrefs

Cf. A171055, A222251.

Programs

PARI

flip69(n) = { for(x=1,n, y=x; v=0; f=0; ln =length(Str(x)); a = vector(ln); forstep(j=ln,1,-1, r = y%10; a[j]=r; if(r==6,a[j] = 9; f=1); if(r==9,a[j] = 6; f=1); y = floor(y/10); ); forstep(j=ln,1,-1, v=v+a[j]*10^(ln-j) ); if(f,print1(v",")); ) }

Python

def has69(s): return '6' in s or '9' in s
def flp69(s): return s.replace("6", "-").replace("9", "6").replace("-", "9")
def aupto(lim):
    return [int(flp69(s)) for s in map(str, range(lim+1)) if has69(s)]
print(aupto(186)) # Michael S. Branicky, Sep 06 2021