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# Style Sheet

Style sheet for contributors

## Format of entries in the OEIS

Entries in the OEIS have a rigid format. Each entry contains some or all of the following fields.

### A-number

The A-number is an A followed by six digits (until we reach A999999). Example:

A005132
• This is the absolute catalog number of the sequence.
• Some sequences also have a 4-digit M-number, such as M1459, which is the number they carried in "The Encyclopedia of Integer Sequences" by N. J. A. Sloane and S. Plouffe, Academic Press, San Diego, CA, 1995.
• Some older sequences also have a 4-digit N-number, such as N0577, which is the number they carried in "A Handbook of Integer Sequences", by N. J. A. Sloane, Academic Press, NY, 1973.

### Name

This gives a brief description or definition of the sequence. Example:

The even numbers.
• In the description, a(n) denotes the n-th term of the sequence and n is a typical subscript.
Example: a(n) = a(n-1) + a(n-3).
• In some cases however n denotes a typical term in the sequence.
Example: Numbers n such that n and n+1 have the same number of divisors.
• Use the notation and spelling as described below.
• Avoid vanity: do not name the sequence after yourself (or your family members, your friends, etc.).
• Prefer concise mathematical definitions when possible.
• When submitting a sequence, once a name has been entered, it might be necessary to make small changes, but for a complete change, e.g., if the original sequence was aborted or withdrawn, do not use the same A-number; please ask for recycling and request a new A-number.

### Data

This field gives the beginning (at least 4 terms) of the sequence. Example:

1, 1, 1, 2, 3, 5, 9, 32, 56, 144, 320, 1458, 3645, 9477, 25515, 131072, 327680, 1114112
• Ideally this field should give enough terms to fill about three lines on the screen—maybe 260 characters including [decimal] digits, signs, commas and whitespaces (spaces and newlines; DO NOT USE tabs). (In the above example no more terms were known when the sequence was created.)
• The sequence may contain negative integers—if the sequence is known to contain negative integers it should be labeled with the Keyword "sign" (i.e., signed sequence); if the sequence is known NOT to contain negative integers it should be labeled with the Keyword "nonn" (i.e., nonnegative sequence).
• When entering a sequence, you may separate the terms by commas or spaces.
• The entries must be integers—represented with base-10 digits {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}.
• If the terms are fractions, then the numerators and denominators should be entered as separate sequences, labeled with the Keyword "frac", and with cross-references connecting the two sequences.
• Only sequences that are well-defined and of general interest should be submitted.
• If every second term is zero (A, 0, B, 0, C, 0, D, 0, E, ...) then normally we omit the zeros and list the sequence as A, B, C, D, E, ...

### Offset

The index of the first term of the sequence. (See examples.) For lists, the offset should be 1 (rather than 0). For arrays and triangles, the offset should be the index of the first row.

• There is a second part to the offset after a comma, which is the 1-based index of the first term which is greater than 1 in absolute value. If all terms are -1, 0, or 1 the second part should be 1.
• You do not need to add this part; the server will calculate it for you.