A357047 - OEIS

A357047

Lexigographically earliest sequence of distinct nonnegative integers such that a(2n)*a(2n+1) has n as substring, for all n >= 0.

0, 1, 2, 5, 3, 4, 6, 22, 7, 12, 8, 19, 9, 14, 10, 17, 11, 18, 13, 15, 16, 63, 20, 55, 21, 58, 23, 31, 24, 59, 25, 46, 26, 62, 27, 64, 28, 65, 29, 66, 30, 34, 32, 38, 33, 37, 35, 67, 36, 68, 39, 75, 40, 315, 41, 47, 42, 69, 43, 103, 44, 70, 45, 71, 48, 84, 49, 117, 50, 268, 51, 85, 52, 93, 53

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

COMMENTS

Could also be defined or read as table with two columns, row k = 0, 1, 2, ... holding (a(2k), a(2k+1)).

LINKS

Table of n, a(n) for n=0..74.

Eric Angelini, Smallest multiplication, personal blog "Cinquante Signes", blogspot.com, Dec. 7, 2022

PROG

(Python)

def A357047_first(N):

S = [] ; used = {-1}; unused = min(used)+1

for n in range(N):

ns = str(n) ; x = unused

for k in range(x+1, 10**9):

if k not in used and ns in str(x*k): break

S += [ x, k ]

used |= { x, k }

while unused in used: used -= { unused-1 }; unused += 1

return S # M. F. Hasler, Dec 07 2022

CROSSREFS

Sequence in context: A065184 A065181 A026258 * A105530 A370932 A245815

Adjacent sequences: A357044 A357045 A357046 * A357048 A357049 A357050

KEYWORD

nonn,base,tabf

AUTHOR

Eric Angelini and M. F. Hasler, Dec 07 2022

STATUS

approved