

A203620


A selfdescribing sequence: when the sequence is read as a string of digits, a(n) says the position of the digits that are prime.


0



2, 3, 5, 1, 7, 8, 22, 11, 20, 15, 21, 14, 23, 25, 26, 27, 29, 31, 32, 19, 35, 36, 37, 39, 40, 41, 49, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 63, 70, 71, 73, 75, 76, 77, 78, 79, 81, 82, 83, 85, 90, 92, 94, 98, 105, 109, 200, 115, 201, 114, 122, 123, 125, 126
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OFFSET

1,1


COMMENTS

Digits in position a(n) are prime, namely 2, 3, 5 or 7. Any step chooses the minimum integer not yet present in the sequence and not leading to a contradiction.


LINKS

Table of n, a(n) for n=1..64.
Index to sequences related to say what you see


EXAMPLE

The sequence cannot start with 1 because the first digit, 1 itself, is not prime. Then let us put 2. The next digit must be prime: 3. Even the third must be prime: 5. No specific indications for the fourth digit. We can choose 1 because the first digit, 2, is prime. The fifth must be prime: 7. And so on.


CROSSREFS

Cf. A121053
Sequence in context: A210945 A191795 A121053 * A249070 A249069 A191308
Adjacent sequences: A203617 A203618 A203619 * A203621 A203622 A203623


KEYWORD

nonn,base


AUTHOR

Paolo P. Lava, Feb 15 2012


STATUS

approved



